[V0 Deprecation] Remove V0 core (#25321)

Signed-off-by: Woosuk Kwon <woosuk@thinkingmachines.ai>
Signed-off-by: Woosuk Kwon <woosuk.kwon@berkeley.edu>

.buildkite/test-pipeline.yaml

@@ -148,7 +148,6 @@ steps:
   num_gpus: 4
   source_file_dependencies:
   - vllm/distributed/
-  - vllm/core/
   - tests/distributed/test_utils
   - tests/distributed/test_pynccl
   - tests/distributed/test_events
@@ -867,8 +866,6 @@ steps:
   - tests/distributed/
   - vllm/compilation
   - vllm/worker/worker_base.py
-  - vllm/worker/worker.py
-  - vllm/worker/model_runner.py
   - entrypoints/llm/test_collective_rpc.py
   - tests/v1/test_async_llm_dp.py
   - tests/v1/test_external_lb_dp.py

.github/CODEOWNERS

@@ -4,10 +4,8 @@
 # This lists cover the "core" components of vLLM that require careful review
 /vllm/attention @LucasWilkinson
 /vllm/attention/backends/abstract.py @WoosukKwon @zhuohan123 @youkaichao @alexm-redhat @comaniac @njhill
-/vllm/core @zhuohan123 @youkaichao @alexm-redhat @comaniac @njhill
 /vllm/executor/executor_base.py @zhuohan123 @youkaichao @alexm-redhat @comaniac @njhill @22quinn
 /vllm/worker/worker_base.py @zhuohan123 @youkaichao @alexm-redhat @comaniac @njhill @22quinn
-/vllm/worker/worker.py @zhuohan123 @youkaichao @alexm-redhat @comaniac @njhill
 /vllm/model_executor/layers/fused_moe @mgoin
 /vllm/model_executor/layers/sampler.py @zhuohan123 @youkaichao @alexm-redhat @comaniac @njhill @NickLucche
 /vllm/model_executor/layers/quantization @mgoin @robertgshaw2-redhat @tlrmchlsmth @yewentao256

pyproject.toml

@@ -70,7 +70,6 @@ line-length = 80
 "vllm/_version.py" = ["ALL"]
 # Python 3.8 typing - skip V0 code
 "vllm/attention/**/*.py" = ["UP006", "UP035"]
-"vllm/core/**/*.py" = ["UP006", "UP035"]
 "vllm/engine/**/*.py" = ["UP006", "UP035"]
 "vllm/executor/**/*.py" = ["UP006", "UP035"]
 "vllm/worker/**/*.py" = ["UP006", "UP035"]
@@ -117,7 +116,6 @@ files = [
     "vllm/*.py",
     "vllm/assets",
     "vllm/entrypoints",
-    "vllm/core",
     "vllm/inputs",
     "vllm/logging_utils",
     "vllm/multimodal",

vllm/attention/backends/differential_flash_attn.py

@@ -4,7 +4,7 @@
 from collections import defaultdict
 from dataclasses import dataclass
 from itertools import accumulate
-from typing import TYPE_CHECKING, Any, Dict, List, Optional, Tuple, Type
+from typing import Any, Dict, List, Optional, Tuple, Type
 
 import torch
 from einops import rearrange
@@ -34,9 +34,6 @@ from vllm.utils import async_tensor_h2d, make_tensor_with_pad
 from vllm.vllm_flash_attn import (flash_attn_varlen_func,
                                   flash_attn_with_kvcache)
 
-if TYPE_CHECKING:
-    from vllm.worker.model_runner import ModelInputForGPUBuilder
-
 logger = init_logger(__name__)
 
 
@@ -329,7 +326,7 @@ class DifferentialFlashAttentionMetadata(AttentionMetadata):
 class DifferentialFlashAttentionMetadataBuilder(
         AttentionMetadataBuilder[DifferentialFlashAttentionMetadata]):
 
-    def __init__(self, input_builder: "ModelInputForGPUBuilder"):
+    def __init__(self, input_builder):
         self.input_builder = input_builder
         self.runner = input_builder.runner
         self.sliding_window = input_builder.sliding_window
@@ -350,9 +347,8 @@ class DifferentialFlashAttentionMetadataBuilder(
         self.num_decode_tokens = 0
         self.has_prefix_cache_hit = False
 
-    def _add_seq_group(
-            self, inter_data: "ModelInputForGPUBuilder.InterDataForSeqGroup",
-            chunked_prefill_enabled: bool, prefix_cache_hit: bool):
+    def _add_seq_group(self, inter_data, chunked_prefill_enabled: bool,
+                       prefix_cache_hit: bool):
         """Add a sequence group to the metadata. Specifically update/append
         1. context length.
         2. block table.

vllm/attention/backends/dual_chunk_flash_attn.py

@@ -4,7 +4,7 @@
 """
 import math
 from dataclasses import dataclass
-from typing import TYPE_CHECKING, Any, Dict, List, Optional, Tuple, Type
+from typing import Any, Dict, List, Optional, Tuple, Type
 
 import torch
 import torch.distributed
@@ -22,9 +22,6 @@ from vllm.utils import async_tensor_h2d
 from vllm.vllm_flash_attn import (flash_attn_varlen_func,
                                   flash_attn_with_kvcache, sparse_attn_func)
 
-if TYPE_CHECKING:
-    from vllm.worker.model_runner import ModelInputForGPUBuilder
-
 logger = init_logger(__name__)
 
 
@@ -224,9 +221,8 @@ class DualChunkFlashAttentionMetadataBuilder(FlashAttentionMetadataBuilder):
         super().prepare()
         self.orig_seq_lens: List[int] = []
 
-    def _add_seq_group(
-            self, inter_data: "ModelInputForGPUBuilder.InterDataForSeqGroup",
-            chunked_prefill_enabled: bool, prefix_cache_hit: bool):
+    def _add_seq_group(self, inter_data, chunked_prefill_enabled: bool,
+                       prefix_cache_hit: bool):
         super()._add_seq_group(inter_data, chunked_prefill_enabled,
                                prefix_cache_hit)
         for prompt_len, seq_len in zip(inter_data.prompt_lens,

vllm/attention/backends/flash_attn.py

@@ -4,7 +4,7 @@
 from collections import defaultdict
 from dataclasses import dataclass
 from itertools import accumulate
-from typing import TYPE_CHECKING, Dict, List, Optional, Tuple, Type
+from typing import Dict, List, Optional, Tuple, Type
 
 import torch
 
@@ -31,9 +31,6 @@ from vllm.utils import async_tensor_h2d, make_tensor_with_pad
 from vllm.vllm_flash_attn import (flash_attn_varlen_func,
                                   flash_attn_with_kvcache)
 
-if TYPE_CHECKING:
-    from vllm.worker.model_runner import ModelInputForGPUBuilder
-
 logger = init_logger(__name__)
 
 
@@ -312,7 +309,7 @@ class FlashAttentionMetadata(AttentionMetadata):
 class FlashAttentionMetadataBuilder(
         AttentionMetadataBuilder[FlashAttentionMetadata]):
 
-    def __init__(self, input_builder: "ModelInputForGPUBuilder"):
+    def __init__(self, input_builder):
         self.input_builder = input_builder
         self.runner = input_builder.runner
         self.sliding_window = input_builder.sliding_window
@@ -332,9 +329,8 @@ class FlashAttentionMetadataBuilder(
         self.num_decode_tokens = 0
         self.has_prefix_cache_hit = False
 
-    def _add_seq_group(
-            self, inter_data: "ModelInputForGPUBuilder.InterDataForSeqGroup",
-            chunked_prefill_enabled: bool, prefix_cache_hit: bool):
+    def _add_seq_group(self, inter_data, chunked_prefill_enabled: bool,
+                       prefix_cache_hit: bool):
         """Add a sequence group to the metadata. Specifically update/append
         1. context length.
         2. block table.

vllm/attention/backends/mla/common.py

@@ -193,8 +193,7 @@ from collections import defaultdict
 from contextlib import contextmanager
 from dataclasses import dataclass
 from itertools import accumulate
-from typing import (TYPE_CHECKING, Any, Dict, Generic, List, Optional, Tuple,
-                    Type, TypeVar)
+from typing import Any, Dict, Generic, List, Optional, Tuple, Type, TypeVar
 
 import torch
 
@@ -233,9 +232,6 @@ except ImportError:
     except ImportError:
         flash_attn_varlen_func = None
 
-if TYPE_CHECKING:
-    from vllm.worker.model_runner import ModelInputForGPUBuilder
-
 is_hip = current_platform.is_rocm()
 
 
@@ -638,7 +634,7 @@ class MLACommonMetadataBuilder(AttentionMetadataBuilder[T], Generic[T]):
     """
     BLOCK_TABLE_EXTENDER: list[list[int]] = []
 
-    def __init__(self, input_builder: "ModelInputForGPUBuilder"):
+    def __init__(self, input_builder):
         self.input_builder = input_builder
         self.runner = input_builder.runner
         self.sliding_window = input_builder.sliding_window
@@ -668,9 +664,8 @@ class MLACommonMetadataBuilder(AttentionMetadataBuilder[T], Generic[T]):
         self.num_decode_tokens = 0
         self.has_prefix_cache_hit = False
 
-    def _add_seq_group(
-            self, inter_data: "ModelInputForGPUBuilder.InterDataForSeqGroup",
-            chunked_prefill_enabled: bool, prefix_cache_hit: bool):
+    def _add_seq_group(self, inter_data, chunked_prefill_enabled: bool,
+                       prefix_cache_hit: bool):
         """Add a sequence group to the metadata. Specifically update/append
         1. context length.
         2. block table.

vllm/attention/backends/placeholder_attn.py

@@ -4,7 +4,7 @@
 from collections import defaultdict
 from dataclasses import dataclass
 from itertools import accumulate
-from typing import TYPE_CHECKING, Dict, List, Optional, Tuple, Type
+from typing import Dict, List, Optional, Tuple, Type
 
 import torch
 
@@ -13,9 +13,6 @@ from vllm.attention.backends.abstract import (AttentionBackend, AttentionImpl,
                                               AttentionMetadataBuilder)
 from vllm.attention.backends.utils import CommonAttentionState
 from vllm.multimodal import MultiModalPlaceholderMap
-
-if TYPE_CHECKING:
-    from vllm.worker.model_runner import (ModelInputForGPUBuilder)
 from vllm.utils import async_tensor_h2d
 
 # Placeholder attention backend for models like Mamba and pooling models that
@@ -204,7 +201,7 @@ class PlaceholderAttentionMetadata(AttentionMetadata):
 class PlaceholderAttentionMetadataBuilder(
         AttentionMetadataBuilder[PlaceholderAttentionMetadata]):
 
-    def __init__(self, input_builder: "ModelInputForGPUBuilder"):
+    def __init__(self, input_builder):
 
         self.input_builder = input_builder
         self.runner = input_builder.runner
@@ -220,9 +217,7 @@ class PlaceholderAttentionMetadataBuilder(
         self.num_prefill_tokens = 0
         self.num_decode_tokens = 0
 
-    def _add_seq_group(
-            self, inter_data: "ModelInputForGPUBuilder.InterDataForSeqGroup",
-            chunked_prefill_enabled: bool):
+    def _add_seq_group(self, inter_data, chunked_prefill_enabled: bool):
         """Add a sequence group to the metadata. Specifically update/append
         1. context length.
         """

vllm/attention/backends/rocm_aiter_mla.py

@@ -3,7 +3,7 @@
 
 from contextlib import contextmanager
 from dataclasses import dataclass
-from typing import TYPE_CHECKING, Optional, Type, Union
+from typing import Optional, Type, Union
 
 import torch
 
@@ -19,9 +19,6 @@ from vllm.attention.backends.utils import (compute_slot_mapping,
 from vllm.attention.ops.rocm_aiter_mla import (aiter_mla_decode_fwd,
                                                get_aiter_mla_metadata)
 
-if TYPE_CHECKING:
-    from vllm.worker.model_runner import ModelInputForGPUBuilder
-
 
 def is_aiter_mla_enabled() -> bool:
     return envs.VLLM_ROCM_USE_AITER \
@@ -110,7 +107,7 @@ class AiterMLAMetadata(MLACommonMetadata):
 class AiterMLAMetadataBuilder(MLACommonMetadataBuilder[AiterMLAMetadata]):
     BLOCK_TABLE_EXTENDER: list[list[int]] = [[]]
 
-    def __init__(self, input_builder: "ModelInputForGPUBuilder"):
+    def __init__(self, input_builder):
         super().__init__(input_builder)
         assert self.block_size == 1, "AITER MLA requires only block size 1."
 

vllm/attention/backends/utils.py

@@ -35,9 +35,6 @@ PAD_SLOT_ID = -1
 # if we have at least this many elements. Could be tuned further.
 _COMPUTE_SLOT_MAPPING_NUMPY_NUMEL = 256
 
-if TYPE_CHECKING:
-    from vllm.worker.model_runner import ModelInputForGPUBuilder
-
 
 def is_block_tables_empty(block_tables: Union[None, Dict]):
     """
@@ -129,7 +126,7 @@ class CommonMetadataBuilder(AttentionMetadataBuilder[TAttentionMetadata]):
 
     _metadata_cls: Type[TAttentionMetadata]
 
-    def __init__(self, input_builder: "ModelInputForGPUBuilder"):
+    def __init__(self, input_builder):
         self.input_builder = input_builder
         self.runner = input_builder.runner
 
@@ -149,9 +146,7 @@ class CommonMetadataBuilder(AttentionMetadataBuilder[TAttentionMetadata]):
         self.num_prefill_tokens = 0
         self.num_decode_tokens = 0
 
-    def _add_seq_group(
-            self, inter_data: "ModelInputForGPUBuilder.InterDataForSeqGroup",
-            chunked_prefill_enabled: bool):
+    def _add_seq_group(self, inter_data, chunked_prefill_enabled: bool):
         is_prompt = inter_data.is_prompt
         block_tables = inter_data.block_tables
 

vllm/core/block/block_table.py

-# SPDX-License-Identifier: Apache-2.0
-# SPDX-FileCopyrightText: Copyright contributors to the vLLM project
-
-import math
-from typing import List, Optional
-
-from vllm.core.block.common import BlockList
-from vllm.core.block.interfaces import Block, DeviceAwareBlockAllocator
-from vllm.utils import Device, cdiv, chunk_list
-
-
-class BlockTable:
-    """A class to manage blocks for a specific sequence.
-
-    The BlockTable maps a sequence of tokens to a list of blocks, where each
-    block represents a contiguous memory allocation for a portion of the 
-    sequence. The blocks are managed by a DeviceAwareBlockAllocator, which is
-    responsible for allocating and freeing memory for the blocks.
-
-    Args:
-        block_size (int): The maximum number of tokens that can be stored in a
-            single block.
-        block_allocator (DeviceAwareBlockAllocator): The block allocator used to
-            manage memory for the blocks.
-        _blocks (Optional[List[Block]], optional): An optional list of existing
-            blocks to initialize the BlockTable with. If not provided, an empty
-            BlockTable is created.
-        max_block_sliding_window (Optional[int], optional): The number of
-            blocks to keep around for each sequence. If None, all blocks
-            are kept (eg., when sliding window is not used).
-            It should at least fit the sliding window size of the model.
-
-    Attributes:
-        _block_size (int): The maximum number of tokens that can be stored in a
-            single block.
-        _allocator (DeviceAwareBlockAllocator): The block allocator used to
-            manage memory for the blocks.
-        _blocks (Optional[List[Block]]): The list of blocks managed by this
-            BlockTable.
-        _num_full_slots (int): The number of tokens currently stored in the
-            blocks.
-    """
-
-    def __init__(
-        self,
-        block_size: int,
-        block_allocator: DeviceAwareBlockAllocator,
-        _blocks: Optional[List[Block]] = None,
-        max_block_sliding_window: Optional[int] = None,
-    ):
-        self._block_size = block_size
-        self._allocator = block_allocator
-        if _blocks is None:
-            _blocks = []
-        self._blocks: BlockList = BlockList(_blocks)
-
-        self._max_block_sliding_window = max_block_sliding_window
-        self._num_full_slots = self._get_num_token_ids()
-
-    @staticmethod
-    def get_num_required_blocks(token_ids: List[int],
-                                block_size: int,
-                                num_lookahead_slots: int = 0) -> int:
-        """Calculates the minimum number of blocks required to store a given
-        sequence of token IDs along with any look-ahead slots that may be
-        required (like in multi-step + chunked-prefill).
-
-        This assumes worst-case scenario, where every block requires a new
-        allocation (e.g. ignoring prefix caching).
-
-        Args:
-            token_ids (List[int]): The sequence of token IDs to be stored.
-            block_size (int): The maximum number of tokens that can be stored in
-                a single block.
-            num_lookahead_slots (int): look-ahead slots that the sequence may
-                require.
-
-        Returns:
-            int: The minimum number of blocks required to store the given
-                sequence of token IDs along with any required look-ahead slots.
-        """
-        return cdiv(len(token_ids) + num_lookahead_slots, block_size)
-
-    def allocate(self,
-                 token_ids: List[int],
-                 device: Device = Device.GPU,
-                 extra_hash: Optional[int] = None) -> None:
-        """Allocates memory blocks for storing the given sequence of token IDs.
-
-        This method allocates the required number of blocks to store the given
-        sequence of token IDs.
-
-        Args:
-            token_ids (List[int]): The sequence of token IDs to be stored.
-            device (Device, optional): The device on which the blocks should be
-                allocated. Defaults to Device.GPU.
-            extra_hash (Optional[int]): The hash value of additional
-                factors, such as adapters, that influence the block hash
-                in the prefixcaching block.
-        """
-        assert not self._is_allocated
-        assert token_ids
-        blocks = self._allocate_blocks_for_token_ids(prev_block=None,
-                                                     token_ids=token_ids,
-                                                     device=device,
-                                                     extra_hash=extra_hash)
-        self.update(blocks)
-        self._num_full_slots = len(token_ids)
-
-    def update(self, blocks: List[Block]) -> None:
-        """Resets the table to the newly provided blocks 
-        (with their corresponding block ids)
-        """
-        self._blocks.update(blocks)
-
-    def append_token_ids(self,
-                         token_ids: List[int],
-                         num_lookahead_slots: int = 0,
-                         num_computed_slots: Optional[int] = None,
-                         extra_hash: Optional[int] = None) -> None:
-        """Appends a sequence of token IDs to the existing blocks in the
-        BlockTable.
-
-        This method appends the given sequence of token IDs to the existing
-        blocks in the BlockTable. If there is not enough space in the existing
-        blocks, new blocks are allocated using the `ensure_num_empty_slots`
-        method to accommodate the additional tokens.
-
-        The token IDs are divided into chunks of size `block_size` (except for
-        the first chunk, which may be smaller), and each chunk is appended to a
-        separate block.
-
-        Args:
-            token_ids (List[int]): The sequence of token IDs to be appended.
-            num_computed_slots (Optional[int]): The number of KV cache slots
-                that are already filled (computed).
-                When sliding window is enabled, this is used to compute how many
-                blocks to drop at the front of the sequence.
-                Without sliding window, None can be passed.
-                Without chunked prefill, it should be the same as
-                _num_full_slots.
-            extra_hash (Optional[int]): The hash value of additional
-                factors such as adapters that influence the block, apart
-                from the token_ids.
-        """
-        assert self._is_allocated, "no blocks have been allocated"
-        assert len(self._blocks) > 0
-
-        # Drop blocks that are no longer needed due to sliding window
-        if self._max_block_sliding_window is not None:
-            null_block = self._allocator.allocate_or_get_null_block()
-            assert num_computed_slots is not None
-            end_block_idx = (num_computed_slots //
-                             self._block_size) - self._max_block_sliding_window
-            for idx in range(0, end_block_idx):
-                b = self._blocks[idx]
-                if b is not null_block:
-                    self._allocator.free(b)
-                    self._blocks[idx] = null_block
-
-        # Ensure there are enough empty slots for the new tokens plus
-        # lookahead slots
-        self.ensure_num_empty_slots(num_empty_slots=len(token_ids) +
-                                    num_lookahead_slots,
-                                    extra_hash=extra_hash)
-
-        # Update the blocks with the new tokens
-        first_block_idx = self._num_full_slots // self._block_size
-        token_blocks = self._chunk_token_blocks_for_append(token_ids)
-
-        for i, token_block in enumerate(token_blocks):
-            self._blocks.append_token_ids(first_block_idx + i, token_block)
-
-        self._num_full_slots += len(token_ids)
-
-    def ensure_num_empty_slots(self,
-                               num_empty_slots: int,
-                               extra_hash: Optional[int] = None) -> None:
-        """Ensures that the BlockTable has at least the specified number of
-        empty slots available.
-
-        This method checks if the BlockTable has enough empty slots (i.e.,
-        available space) to accommodate the requested number of tokens. If not,
-        it allocates additional blocks on the GPU to ensure that the required
-        number of empty slots is available.
-
-        Args:
-            num_empty_slots (int): The minimum number of empty slots required.
-            extra_hash (Optional[int]): The hash value of additional
-                factors such as adapters that influence the block, apart
-                from the token_ids.
-        """
-        # Currently the block table only supports
-        # appending tokens to GPU blocks.
-        device = Device.GPU
-        assert self._is_allocated
-
-        if self._num_empty_slots >= num_empty_slots:
-            return
-
-        slots_to_allocate = num_empty_slots - self._num_empty_slots
-        blocks_to_allocate = cdiv(slots_to_allocate, self._block_size)
-
-        for _ in range(blocks_to_allocate):
-            assert len(self._blocks) > 0
-            self._blocks.append(
-                self._allocator.allocate_mutable_block(
-                    prev_block=self._blocks[-1],
-                    device=device,
-                    extra_hash=extra_hash))
-
-    def fork(self) -> "BlockTable":
-        """Creates a new BlockTable instance with a copy of the blocks from the
-        current instance.
-
-        This method creates a new BlockTable instance with the same block size,
-        block allocator, and a copy of the blocks from the current instance. The
-        new BlockTable has its own independent set of blocks, but shares the
-        same underlying memory allocation with the original BlockTable.
-
-        Returns:
-            BlockTable: A new BlockTable instance with a copy of the blocks from
-                the current instance.
-        """
-        assert self._is_allocated
-        assert len(self._blocks) > 0
-        forked_blocks = self._allocator.fork(self._blocks[-1])
-        return BlockTable(
-            block_size=self._block_size,
-            block_allocator=self._allocator,
-            _blocks=forked_blocks,
-            max_block_sliding_window=self._max_block_sliding_window,
-        )
-
-    def free(self) -> None:
-        """Frees the memory occupied by the blocks in the BlockTable.
-
-        This method iterates over all the blocks in the `_blocks` list and calls
-        the `free` method of the `_allocator` object to release the memory
-        occupied by each block. After freeing all the blocks, the `_blocks` list
-        is set to `None`.
-        """
-        for block in self.blocks:
-            self._allocator.free(block)
-        self._blocks.reset()
-
-    @property
-    def physical_block_ids(self) -> List[int]:
-        """Returns a list of physical block indices for the blocks in the
-        BlockTable.
-
-        This property returns a list of integers, where each integer represents
-        the physical block index of a corresponding block in the `_blocks` list.
-        The physical block index is a unique identifier for the memory location
-        occupied by the block.
-
-        Returns:
-            List[int]: A list of physical block indices for the blocks in the
-                BlockTable.
-        """
-        return self._blocks.ids()
-
-    def get_unseen_token_ids(self, sequence_token_ids: List[int]) -> List[int]:
-        """Get the number of "unseen" tokens in the sequence.
-
-        Unseen tokens are tokens in the sequence corresponding to this block
-        table, but are not yet appended to this block table.
-
-        Args:
-            sequence_token_ids (List[int]): The list of token ids in the
-                sequence.
-
-        Returns:
-            List[int]: The postfix of sequence_token_ids that has not yet been
-                appended to the block table.
-        """
-
-        # Since the block table is append-only, the unseen token ids are the
-        # ones after the appended ones.
-        return sequence_token_ids[self.num_full_slots:]
-
-    def _allocate_blocks_for_token_ids(
-            self,
-            prev_block: Optional[Block],
-            token_ids: List[int],
-            device: Device,
-            extra_hash: Optional[int] = None) -> List[Block]:
-        blocks: List[Block] = []
-
-        block_token_ids = []
-        tail_token_ids = []
-        for cur_token_ids in chunk_list(token_ids, self._block_size):
-            if len(cur_token_ids) == self._block_size:
-                block_token_ids.append(cur_token_ids)
-            else:
-                tail_token_ids.append(cur_token_ids)
-
-        if block_token_ids:
-            blocks.extend(
-                self._allocator.allocate_immutable_blocks(
-                    prev_block,
-                    block_token_ids=block_token_ids,
-                    device=device,
-                    extra_hash=extra_hash))
-            prev_block = blocks[-1]
-
-        if tail_token_ids:
-            assert len(tail_token_ids) == 1
-            cur_token_ids = tail_token_ids[0]
-
-            block = self._allocator.allocate_mutable_block(
-                prev_block=prev_block, device=device, extra_hash=extra_hash)
-            block.append_token_ids(cur_token_ids)
-
-            blocks.append(block)
-
-        return blocks
-
-    def _get_all_token_ids(self) -> List[int]:
-        # NOTE: This function is O(seq_len); use sparingly.
-        token_ids: List[int] = []
-
-        if not self._is_allocated:
-            return token_ids
-
-        for block in self.blocks:
-            token_ids.extend(block.token_ids)
-
-        return token_ids
-
-    def _get_num_token_ids(self) -> int:
-        res = 0
-        for block in self.blocks:
-            res += len(block.token_ids)
-
-        return res
-
-    @property
-    def _is_allocated(self) -> bool:
-        return len(self._blocks) > 0
-
-    @property
-    def blocks(self) -> List[Block]:
-        return self._blocks.list()
-
-    @property
-    def _num_empty_slots(self) -> int:
-        assert self._is_allocated
-        return len(self._blocks) * self._block_size - self._num_full_slots
-
-    @property
-    def num_full_slots(self) -> int:
-        """Returns the total number of tokens currently stored in the
-        BlockTable.
-
-        Returns:
-            int: The total number of tokens currently stored in the BlockTable.
-        """
-        return self._num_full_slots
-
-    def get_num_blocks_touched_by_append_slots(
-            self, token_ids: List[int], num_lookahead_slots: int) -> int:
-        """Determine how many blocks will be "touched" by appending the token
-        ids.
-
-        This is required for the scheduler to determine whether a sequence can
-        continue generation, or if it must be preempted.
-        """
-        # Math below is equivalent to:
-        # all_token_ids = token_ids + [-1] * num_lookahead_slots
-        # token_blocks = self._chunk_token_blocks_for_append(all_token_ids)
-        # return len(token_blocks)
-
-        num_token_ids = len(token_ids) + num_lookahead_slots
-        first_chunk_size = self._block_size - (self._num_full_slots %
-                                               self._block_size)
-        num_token_blocks = (1 + math.ceil(
-            (num_token_ids - first_chunk_size) / self._block_size))
-        return num_token_blocks
-
-    def _chunk_token_blocks_for_append(
-            self, token_ids: List[int]) -> List[List[int]]:
-        """Split the token ids into block-sized chunks so they can be easily
-        appended to blocks. The first such "token block" may have less token ids
-        than the block size, since the last allocated block may be partially
-        full.
-
-        If no token ids are provided, then no chunks are returned.
-        """
-
-        if not token_ids:
-            return []
-
-        first_chunk_size = self._block_size - (self._num_full_slots %
-                                               self._block_size)
-        token_blocks = [token_ids[:first_chunk_size]]
-        token_blocks.extend(
-            chunk_list(token_ids[first_chunk_size:], self._block_size))
-        return token_blocks

vllm/core/block/common.py

-# SPDX-License-Identifier: Apache-2.0
-# SPDX-FileCopyrightText: Copyright contributors to the vLLM project
-
-from collections import deque
-from dataclasses import dataclass
-from typing import Deque, Dict, Iterable, List, Optional, Protocol, Tuple
-
-from vllm.core.block.interfaces import Block, BlockAllocator
-
-BlockId = int
-RefCount = int
-
-
-class RefCounterProtocol(Protocol):
-
-    def incr(self, block_id: BlockId) -> RefCount:
-        raise NotImplementedError
-
-    def decr(self, block_id: BlockId) -> RefCount:
-        raise NotImplementedError
-
-    def get(self, block_id: BlockId) -> RefCount:
-        raise NotImplementedError
-
-
-class RefCounter(RefCounterProtocol):
-    """A class for managing reference counts for a set of block indices.
-
-    The RefCounter class maintains a dictionary that maps block indices to their
-    corresponding reference counts. It provides methods to increment, decrement,
-    and retrieve the reference count for a given block index.
-
-    Args:
-        all_block_indices (Iterable[BlockId]): An iterable of block indices
-            to initialize the reference counter with.
-    """
-
-    def __init__(self, all_block_indices: Iterable[BlockId]):
-        deduped = set(all_block_indices)
-        self._refcounts: Dict[BlockId, RefCount] = {
-            index: 0
-            for index in deduped
-        }
-
-    def incr(self, block_id: BlockId) -> RefCount:
-        assert block_id in self._refcounts
-        pre_incr_refcount = self._refcounts[block_id]
-
-        assert pre_incr_refcount >= 0
-
-        post_incr_refcount = pre_incr_refcount + 1
-        self._refcounts[block_id] = post_incr_refcount
-        return post_incr_refcount
-
-    def decr(self, block_id: BlockId) -> RefCount:
-        assert block_id in self._refcounts
-        refcount = self._refcounts[block_id]
-
-        assert refcount > 0
-        refcount -= 1
-
-        self._refcounts[block_id] = refcount
-
-        return refcount
-
-    def get(self, block_id: BlockId) -> RefCount:
-        assert block_id in self._refcounts
-        return self._refcounts[block_id]
-
-    def as_readonly(self) -> "ReadOnlyRefCounter":
-        return ReadOnlyRefCounter(self)
-
-
-class ReadOnlyRefCounter(RefCounterProtocol):
-    """A read-only view of the RefCounter class.
-
-    The ReadOnlyRefCounter class provides a read-only interface to access the
-    reference counts maintained by a RefCounter instance. It does not allow
-    modifications to the reference counts.
-
-    Args:
-        refcounter (RefCounter): The RefCounter instance to create a read-only
-            view for.
-    """
-
-    def __init__(self, refcounter: RefCounter):
-        self._refcounter = refcounter
-
-    def incr(self, block_id: BlockId) -> RefCount:
-        raise ValueError("Incr not allowed")
-
-    def decr(self, block_id: BlockId) -> RefCount:
-        raise ValueError("Decr not allowed")
-
-    def get(self, block_id: BlockId) -> RefCount:
-        return self._refcounter.get(block_id)
-
-
-class CopyOnWriteTracker:
-    """A class for tracking and managing copy-on-write operations for blocks.
-
-    The CopyOnWriteTracker class maintains a mapping of source block indices to
-        their corresponding copy-on-write destination block indices. It works in
-        conjunction with a RefCounter.
-
-    Args:
-        refcounter (RefCounter): The reference counter used to track block
-            reference counts.
-    """
-
-    def __init__(self, refcounter: RefCounterProtocol):
-        self._copy_on_writes: List[Tuple[BlockId, BlockId]] = []
-        self._refcounter = refcounter
-
-    def is_appendable(self, block: Block) -> bool:
-        """Checks if the block is shared or not. If shared, then it cannot
-        be appended and needs to be duplicated via copy-on-write
-        """
-        block_id = block.block_id
-        if block_id is None:
-            return True
-
-        refcount = self._refcounter.get(block_id)
-        return refcount <= 1
-
-    def record_cow(self, src_block_id: Optional[BlockId],
-                   trg_block_id: Optional[BlockId]) -> None:
-        """Records a copy-on-write operation from source to target block id
-        Args:
-            src_block_id (BlockId): The source block id from which to copy 
-                the data
-            trg_block_id (BlockId): The target block id to which the data
-                is copied
-        """
-        assert src_block_id is not None
-        assert trg_block_id is not None
-        self._copy_on_writes.append((src_block_id, trg_block_id))
-
-    def clear_cows(self) -> List[Tuple[BlockId, BlockId]]:
-        """Clears the copy-on-write tracking information and returns the current
-        state.
-
-        This method returns a list mapping source block indices to
-         destination block indices for the current copy-on-write operations.
-        It then clears the internal tracking information.
-
-        Returns:
-            List[Tuple[BlockId, BlockId]]: A list mapping source
-                block indices to destination block indices for the
-                current copy-on-write operations.
-        """
-        cows = self._copy_on_writes
-        self._copy_on_writes = []
-        return cows
-
-
-class BlockPool:
-    """Used to pre-allocate block objects, in order to avoid excessive python
-    object allocations/deallocations.
-    The pool starts from "pool_size" objects and will increase to more objects
-    if necessary
-
-    Note that multiple block objects may point to the same physical block id,
-    which is why this pool is needed, so that it will be easier to support
-    prefix caching and more complicated sharing of physical blocks.
-    """
-
-    def __init__(self, block_size: int, create_block: Block.Factory,
-                 allocator: BlockAllocator, pool_size: int):
-        self._block_size = block_size
-        self._create_block = create_block
-        self._allocator = allocator
-        self._pool_size = pool_size
-        assert self._pool_size >= 0
-
-        self._free_ids: Deque[int] = deque(range(self._pool_size))
-        self._pool = []
-        for i in range(self._pool_size):
-            self._pool.append(
-                self._create_block(prev_block=None,
-                                   token_ids=[],
-                                   block_size=self._block_size,
-                                   allocator=self._allocator,
-                                   block_id=None,
-                                   extra_hash=None))
-
-    def increase_pool(self):
-        """Doubles the internal pool size
-        """
-        cur_pool_size = self._pool_size
-        new_pool_size = cur_pool_size * 2
-        self._pool_size = new_pool_size
-
-        self._free_ids += deque(range(cur_pool_size, new_pool_size))
-
-        for i in range(cur_pool_size, new_pool_size):
-            self._pool.append(
-                self._create_block(prev_block=None,
-                                   token_ids=[],
-                                   block_size=self._block_size,
-                                   allocator=self._allocator,
-                                   block_id=None,
-                                   extra_hash=None))
-
-    def init_block(self,
-                   prev_block: Optional[Block],
-                   token_ids: List[int],
-                   block_size: int,
-                   physical_block_id: Optional[int],
-                   extra_hash: Optional[int] = None) -> Block:
-        if len(self._free_ids) == 0:
-            self.increase_pool()
-            assert len(self._free_ids) > 0
-
-        pool_id = self._free_ids.popleft()
-
-        block = self._pool[pool_id]
-        block.__init__(  # type: ignore[misc]
-            prev_block=prev_block,
-            token_ids=token_ids,
-            block_size=block_size,
-            allocator=block._allocator,  # type: ignore[attr-defined] 
-            block_id=physical_block_id,
-            extra_hash=extra_hash)
-        block.pool_id = pool_id  # type: ignore[attr-defined]
-        return block
-
-    def free_block(self, block: Block) -> None:
-        self._free_ids.appendleft(block.pool_id)  # type: ignore[attr-defined]
-
-
-class BlockList:
-    """This class is an optimization to allow fast-access to physical 
-    block ids. It maintains a block id list that is updated with the 
-    block list and this avoids the need to reconstruct the block id 
-    list on every iteration of the block manager
-    """
-
-    def __init__(self, blocks: List[Block]):
-        self._blocks: List[Block] = []
-        self._block_ids: List[int] = []
-
-        self.update(blocks)
-
-    def _add_block_id(self, block_id: Optional[BlockId]) -> None:
-        assert block_id is not None
-        self._block_ids.append(block_id)
-
-    def _update_block_id(self, block_index: int,
-                         new_block_id: Optional[BlockId]) -> None:
-        assert new_block_id is not None
-        self._block_ids[block_index] = new_block_id
-
-    def update(self, blocks: List[Block]):
-        self._blocks = blocks
-
-        # Cache block ids for fast query
-        self._block_ids = []
-        for block in self._blocks:
-            self._add_block_id(block.block_id)
-
-    def append_token_ids(self, block_index: int, token_ids: List[int]) -> None:
-        block = self._blocks[block_index]
-        prev_block_id = block.block_id
-
-        block.append_token_ids(token_ids)
-
-        # CoW or promotion may update the internal block_id
-        if prev_block_id != block.block_id:
-            self._update_block_id(block_index, block.block_id)
-
-    def append(self, new_block: Block):
-        self._blocks.append(new_block)
-        self._add_block_id(new_block.block_id)
-
-    def __len__(self) -> int:
-        return len(self._blocks)
-
-    def __getitem__(self, block_index: int) -> Block:
-        return self._blocks[block_index]
-
-    def __setitem__(self, block_index: int, new_block: Block) -> None:
-        self._blocks[block_index] = new_block
-        self._update_block_id(block_index, new_block.block_id)
-
-    def reset(self):
-        self._blocks = []
-        self._block_ids = []
-
-    def list(self) -> List[Block]:
-        return self._blocks
-
-    def ids(self) -> List[int]:
-        return self._block_ids
-
-
-@dataclass
-class CacheMetricData:
-    """A utility dataclass to maintain cache metric.
-    To avoid overflow, we maintain the hit rate in block granularity, so that
-    we can maintain a single hit rate for n_completed_block x block_size,
-    and calculate the real time hit rate by the following:
-    BS = The number of queries per block.
-    nB = The number of completed blocks.
-    HR = hit rate of (nB x BS) queries.
-    Q = current number of queries (< BS).
-    H = current number of hits (< BS).
-    hit rate = ((HR x nB) + (H / Q) x (Q / BS)) / (nB + Q / BS)
-    """
-    num_completed_blocks: int = 0
-    completed_block_cache_hit_rate: float = 0.0
-    num_incompleted_block_queries: int = 0
-    num_incompleted_block_hit: int = 0
-    block_size: int = 1000
-
-    def query(self, hit: bool):
-        self.num_incompleted_block_queries += 1
-        self.num_incompleted_block_hit += 1 if hit else 0
-
-        # When a block is completed, update the cache hit rate
-        # and reset the incomplete numbers.
-        if self.num_incompleted_block_queries == self.block_size:
-            hit_rate = (self.num_incompleted_block_hit /
-                        self.num_incompleted_block_queries)
-            self.completed_block_cache_hit_rate = (
-                self.completed_block_cache_hit_rate * self.num_completed_blocks
-                + hit_rate) / (self.num_completed_blocks + 1)
-            self.num_incompleted_block_queries = 0
-            self.num_incompleted_block_hit = 0
-            self.num_completed_blocks += 1
-
-    def get_hit_rate(self):
-        incomplete_ratio = self.num_incompleted_block_queries / self.block_size
-        total_blocks = self.num_completed_blocks + incomplete_ratio
-        if total_blocks == 0:
-            return 0.0
-
-        completed_block_hit, incompleted_block_hit = 0.0, 0.0
-        if self.num_completed_blocks > 0:
-            completed_block_hit = (self.completed_block_cache_hit_rate *
-                                   self.num_completed_blocks)
-        if self.num_incompleted_block_queries > 0:
-            incompleted_hit_rate = (self.num_incompleted_block_hit /
-                                    self.num_incompleted_block_queries)
-            incompleted_block_hit = (incompleted_hit_rate * incomplete_ratio)
-        return (completed_block_hit + incompleted_block_hit) / total_blocks
-
-
-def get_all_blocks_recursively(last_block: Block) -> List[Block]:
-    """Retrieves all the blocks in a sequence starting from the last block.
-
-    This function recursively traverses the sequence of blocks in reverse order,
-    starting from the given last block, and returns a list of all the blocks in
-    the sequence.
-
-    Args:
-        last_block (Block): The last block in the sequence.
-
-    Returns:
-        List[Block]: A list of all the blocks in the sequence, in the order they
-            appear.
-    """
-
-    def recurse(block: Block, lst: List[Block]) -> None:
-        if block.prev_block is not None:
-            recurse(block.prev_block, lst)
-        lst.append(block)
-
-    all_blocks: List[Block] = []
-    recurse(last_block, all_blocks)
-    return all_blocks

vllm/core/block/cpu_gpu_block_allocator.py

-# SPDX-License-Identifier: Apache-2.0
-# SPDX-FileCopyrightText: Copyright contributors to the vLLM project
-
-from typing import Dict, FrozenSet, List, Optional, Tuple
-
-from vllm.core.block.interfaces import (Block, BlockAllocator, BlockId,
-                                        DeviceAwareBlockAllocator)
-from vllm.core.block.naive_block import NaiveBlock, NaiveBlockAllocator
-from vllm.core.block.prefix_caching_block import PrefixCachingBlockAllocator
-from vllm.utils import Device
-
-
-class CpuGpuBlockAllocator(DeviceAwareBlockAllocator):
-    """A block allocator that can allocate blocks on both CPU and GPU memory.
-
-    This class implements the `DeviceAwareBlockAllocator` interface and provides
-    functionality for allocating and managing blocks of memory on both CPU and
-    GPU devices.
-
-    The `CpuGpuBlockAllocator` maintains separate memory pools for CPU and GPU
-    blocks, and allows for allocation, deallocation, forking, and swapping of
-    blocks across these memory pools.
-    """
-
-    @staticmethod
-    def create(
-        allocator_type: str,
-        num_gpu_blocks: int,
-        num_cpu_blocks: int,
-        block_size: int,
-    ) -> DeviceAwareBlockAllocator:
-        """Creates a CpuGpuBlockAllocator instance with the specified
-        configuration.
-
-        This static method creates and returns a CpuGpuBlockAllocator instance
-        based on the provided parameters. It initializes the CPU and GPU block
-        allocators with the specified number of blocks, block size, and
-        allocator type.
-
-        Args:
-            allocator_type (str): The type of block allocator to use for CPU
-                and GPU blocks. Currently supported values are "naive" and
-                "prefix_caching".
-            num_gpu_blocks (int): The number of blocks to allocate for GPU
-                memory.
-            num_cpu_blocks (int): The number of blocks to allocate for CPU
-                memory.
-            block_size (int): The size of each block in number of tokens.
-
-        Returns:
-            DeviceAwareBlockAllocator: A CpuGpuBlockAllocator instance with the
-                specified configuration.
-
-        Notes:
-            - The block IDs are assigned contiguously, with GPU block IDs coming
-                before CPU block IDs.
-        """
-        reserved_blocks = 0
-        block_ids = list(
-            range(reserved_blocks, num_gpu_blocks + num_cpu_blocks))
-        num_gpu_blocks -= reserved_blocks
-        gpu_block_ids = block_ids[:num_gpu_blocks]
-        cpu_block_ids = block_ids[num_gpu_blocks:]
-
-        if allocator_type == "naive":
-            gpu_allocator: BlockAllocator = NaiveBlockAllocator(
-                create_block=NaiveBlock,  # type: ignore
-                num_blocks=num_gpu_blocks,
-                block_size=block_size,
-                block_ids=gpu_block_ids,
-            )
-
-            cpu_allocator: BlockAllocator = NaiveBlockAllocator(
-                create_block=NaiveBlock,  # type: ignore
-                num_blocks=num_cpu_blocks,
-                block_size=block_size,
-                block_ids=cpu_block_ids,
-            )
-        elif allocator_type == "prefix_caching":
-            gpu_allocator = PrefixCachingBlockAllocator(
-                num_blocks=num_gpu_blocks,
-                block_size=block_size,
-                block_ids=gpu_block_ids,
-            )
-
-            cpu_allocator = PrefixCachingBlockAllocator(
-                num_blocks=num_cpu_blocks,
-                block_size=block_size,
-                block_ids=cpu_block_ids,
-            )
-        else:
-            raise ValueError(f"Unknown allocator type {allocator_type=}")
-
-        return CpuGpuBlockAllocator(
-            cpu_block_allocator=cpu_allocator,
-            gpu_block_allocator=gpu_allocator,
-        )
-
-    def __init__(self, cpu_block_allocator: BlockAllocator,
-                 gpu_block_allocator: BlockAllocator):
-        assert not (
-            cpu_block_allocator.all_block_ids
-            & gpu_block_allocator.all_block_ids
-        ), "cpu and gpu block allocators can't have intersection of block ids"
-
-        self._allocators = {
-            Device.CPU: cpu_block_allocator,
-            Device.GPU: gpu_block_allocator,
-        }
-
-        self._swap_mapping: Dict[int, int] = {}
-        self._null_block: Optional[Block] = None
-
-        self._block_ids_to_allocator: Dict[int, BlockAllocator] = {}
-        for _, allocator in self._allocators.items():
-            for block_id in allocator.all_block_ids:
-                self._block_ids_to_allocator[block_id] = allocator
-
-    def allocate_or_get_null_block(self) -> Block:
-        if self._null_block is None:
-            self._null_block = NullBlock(
-                self.allocate_mutable_block(None, Device.GPU))
-        return self._null_block
-
-    def allocate_mutable_block(self,
-                               prev_block: Optional[Block],
-                               device: Device,
-                               extra_hash: Optional[int] = None) -> Block:
-        """Allocates a new mutable block on the specified device.
-
-        Args:
-            prev_block (Optional[Block]): The previous block to in the sequence.
-                Used for prefix hashing.
-            device (Device): The device on which to allocate the new block.
-            extra_hash (Optional[int]): The hash value of additional
-                factors, such as adapters, that influence the block hash
-                in the prefix caching block.
-
-        Returns:
-            Block: The newly allocated mutable block.
-        """
-        return self._allocators[device].allocate_mutable_block(
-            prev_block, extra_hash=extra_hash)
-
-    def allocate_immutable_blocks(
-            self,
-            prev_block: Optional[Block],
-            block_token_ids: List[List[int]],
-            device: Device,
-            extra_hash: Optional[int] = None) -> List[Block]:
-        """Allocates a new group of immutable blocks with the provided block 
-        token IDs on the specified device.
-
-        Args:
-            prev_block (Optional[Block]): The previous block in the sequence.
-                Used for prefix hashing.
-            block_token_ids (List[int]): The list of block token IDs to be 
-                stored in the new blocks.
-            device (Device): The device on which to allocate the new block.
-            extra_hash (Optional[int]): The hash value of additional
-                factors, such as adapters, that influence the block hash
-                in the prefix caching block.
-
-        Returns:
-            List[Block]: The newly allocated list of immutable blocks 
-                containing the provided block token IDs.
-        """
-        return self._allocators[device].allocate_immutable_blocks(
-            prev_block, block_token_ids, extra_hash=extra_hash)
-
-    def allocate_immutable_block(self,
-                                 prev_block: Optional[Block],
-                                 token_ids: List[int],
-                                 device: Device,
-                                 extra_hash: Optional[int] = None) -> Block:
-        """Allocates a new immutable block with the provided token IDs on the
-        specified device.
-
-        Args:
-            prev_block (Optional[Block]): The previous block in the sequence.
-                Used for prefix hashing.
-            token_ids (List[int]): The list of token IDs to be stored in the new
-                block.
-            device (Device): The device on which to allocate the new block.
-            extra_hash (Optional[int]): The hash value of additional
-                factors, such as adapters, that influence the block hash
-                in the prefix caching block.
-
-        Returns:
-            Block: The newly allocated immutable block containing the provided
-                token IDs.
-        """
-        return self._allocators[device].allocate_immutable_block(
-            prev_block, token_ids, extra_hash=extra_hash)
-
-    def free(self, block: Block) -> None:
-        """Frees the memory occupied by the given block.
-
-        Args:
-            block (Block): The block to be freed.
-        """
-        # Null block should never be freed
-        if isinstance(block, NullBlock):
-            return
-        block_id = block.block_id
-        assert block_id is not None
-        allocator = self._block_ids_to_allocator[block_id]
-        allocator.free(block)
-
-    def fork(self, last_block: Block) -> List[Block]:
-        """Creates a new sequence of blocks that shares the same underlying
-            memory as the original sequence.
-
-        Args:
-            last_block (Block): The last block in the original sequence.
-
-        Returns:
-            List[Block]: A new list of blocks that shares the same memory as the
-                original sequence.
-        """
-        # do not attempt to fork the null block
-        assert not isinstance(last_block, NullBlock)
-        block_id = last_block.block_id
-        assert block_id is not None
-        allocator = self._block_ids_to_allocator[block_id]
-        return allocator.fork(last_block)
-
-    def get_num_free_blocks(self, device: Device) -> int:
-        """Returns the number of free blocks available on the specified device.
-
-        Args:
-            device (Device): The device for which to query the number of free
-                blocks. AssertionError is raised if None is passed.
-
-        Returns:
-            int: The number of free blocks available on the specified device.
-        """
-        return self._allocators[device].get_num_free_blocks()
-
-    def get_num_total_blocks(self, device: Device) -> int:
-        return self._allocators[device].get_num_total_blocks()
-
-    def get_physical_block_id(self, device: Device, absolute_id: int) -> int:
-        """Returns the zero-offset block id on certain device given the 
-        absolute block id.
-
-        Args:
-            device (Device): The device for which to query relative block id.
-                absolute_id (int): The absolute block id for the block in 
-                whole allocator.
-
-        Returns:
-            int: The zero-offset block id on certain device.
-        """
-        return self._allocators[device].get_physical_block_id(absolute_id)
-
-    def swap(self, blocks: List[Block], src_device: Device,
-             dst_device: Device) -> Dict[int, int]:
-        """Execute the swap for the given blocks from source_device
-        on to dest_device, save the current swap mapping and append 
-        them to the accumulated `self._swap_mapping` for each 
-        scheduling move.
-
-        Args:
-            blocks: List of blocks to be swapped.
-            src_device (Device): Device to swap the 'blocks' from.
-            dst_device (Device): Device to swap the 'blocks' to.
-        
-        Returns:
-            Dict[int, int]: Swap mapping from source_device
-                on to dest_device.
-        """
-        src_block_ids = [block.block_id for block in blocks]
-        self._allocators[src_device].swap_out(blocks)
-        self._allocators[dst_device].swap_in(blocks)
-        dst_block_ids = [block.block_id for block in blocks]
-
-        current_swap_mapping: Dict[int, int] = {}
-        for src_block_id, dst_block_id in zip(src_block_ids, dst_block_ids):
-            if src_block_id is not None and dst_block_id is not None:
-                self._swap_mapping[src_block_id] = dst_block_id
-                current_swap_mapping[src_block_id] = dst_block_id
-        return current_swap_mapping
-
-    def get_num_full_blocks_touched(self, blocks: List[Block],
-                                    device: Device) -> int:
-        """Returns the number of full blocks that will be touched by
-        swapping in/out the given blocks on to the 'device'.
-
-        Args:
-            blocks: List of blocks to be swapped.
-            device (Device): Device to swap the 'blocks' on.
-
-        Returns:
-            int: the number of full blocks that will be touched by
-                swapping in/out the given blocks on to the 'device'.
-                Non full blocks are ignored when deciding the number
-                of blocks to touch.
-        """
-        return self._allocators[device].get_num_full_blocks_touched(blocks)
-
-    def clear_copy_on_writes(self) -> List[Tuple[int, int]]:
-        """Clears the copy-on-write (CoW) state and returns the mapping of
-            source to destination block IDs.
-
-        Returns:
-            List[Tuple[int, int]]: A list mapping source block IDs to 
-                destination block IDs.
-        """
-        # CoW only supported on GPU
-        device = Device.GPU
-        return self._allocators[device].clear_copy_on_writes()
-
-    def mark_blocks_as_accessed(self, block_ids: List[int],
-                                now: float) -> None:
-        """Mark blocks as accessed, only use for prefix caching."""
-        # Prefix caching only supported on GPU.
-        device = Device.GPU
-        return self._allocators[device].mark_blocks_as_accessed(block_ids, now)
-
-    def mark_blocks_as_computed(self, block_ids: List[int]) -> None:
-        """Mark blocks as accessed, only use for prefix caching."""
-        # Prefix caching only supported on GPU.
-        device = Device.GPU
-        return self._allocators[device].mark_blocks_as_computed(block_ids)
-
-    def get_common_computed_block_ids(
-            self, computed_seq_block_ids: List[List[int]]) -> List[int]:
-        # Prefix caching only supported on GPU.
-        device = Device.GPU
-        return self._allocators[device].get_common_computed_block_ids(
-            computed_seq_block_ids)
-
-    @property
-    def all_block_ids(self) -> FrozenSet[int]:
-        return frozenset(self._block_ids_to_allocator.keys())
-
-    def get_prefix_cache_hit_rate(self, device: Device) -> float:
-        """Prefix cache hit rate. -1 means not supported or disabled."""
-        assert device in self._allocators
-        return self._allocators[device].get_prefix_cache_hit_rate()
-
-    def reset_prefix_cache(self, device: Optional[Device] = None) -> bool:
-        """Reset prefix cache for specified or all devices."""
-        if device:
-            return self._allocators[device].reset_prefix_cache()
-        success = True
-        for allocator in self._allocators.values():
-            success = success and allocator.reset_prefix_cache()
-        return success
-
-    def get_and_reset_swaps(self) -> List[Tuple[int, int]]:
-        """Returns and clears the mapping of source to destination block IDs.
-        Will be called after every swapping operations for now, and after every
-        schedule when BlockManagerV2 become default. Currently not useful.
-
-        Returns:
-            List[Tuple[int, int]]: A mapping of source to destination block IDs.
-        """
-        mapping = self._swap_mapping.copy()
-        self._swap_mapping.clear()
-        return list(mapping.items())
-
-    def find_cached_blocks_prefix(
-        self,
-        block_hashes: List[int],
-        device: Device = Device.GPU,
-    ) -> List[int]:
-        return self._allocators[device].find_cached_blocks_prefix(block_hashes)
-
-
-class NullBlock(Block):
-    """
-    Null blocks are used as a placeholders for KV cache blocks that have
-    been dropped due to sliding window.
-    This implementation just wraps an ordinary block and prevents it from
-    being modified. It also allows for testing if a block is NullBlock
-    via isinstance().
-    """
-
-    def __init__(self, proxy: Block):
-        super().__init__()
-        self._proxy = proxy
-
-    def append_token_ids(self, token_ids: List[BlockId]):
-        raise ValueError("null block should not be modified")
-
-    @property
-    def block_id(self):
-        return self._proxy.block_id
-
-    @block_id.setter
-    def block_id(self, value: Optional[BlockId]):
-        raise ValueError("null block should not be modified")
-
-    @property
-    def token_ids(self) -> List[BlockId]:
-        return self._proxy.token_ids
-
-    @property
-    def num_tokens_total(self) -> int:
-        raise NotImplementedError(
-            "num_tokens_total is not used for null block")
-
-    @property
-    def num_empty_slots(self) -> BlockId:
-        return self._proxy.num_empty_slots
-
-    @property
-    def is_full(self):
-        return self._proxy.is_full
-
-    @property
-    def prev_block(self):
-        return self._proxy.prev_block
-
-    @property
-    def extra_hash(self):
-        return None
-
-    @property
-    def computed(self):
-        return self._proxy.computed
-
-    @computed.setter
-    def computed(self, value):
-        self._proxy.computed = value
-
-    @property
-    def last_accessed(self) -> float:
-        return self._proxy.last_accessed
-
-    @last_accessed.setter
-    def last_accessed(self, last_accessed_ts: float):
-        self._proxy.last_accessed = last_accessed_ts
-
-    @property
-    def content_hash(self):
-        return self._proxy.content_hash

vllm/core/block/interfaces.py

-# SPDX-License-Identifier: Apache-2.0
-# SPDX-FileCopyrightText: Copyright contributors to the vLLM project
-
-from abc import ABC, abstractmethod
-from typing import Dict, FrozenSet, List, Optional, Protocol, Tuple
-
-from vllm.utils import Device
-
-BlockId = int
-
-
-class Block(ABC):
-
-    @abstractmethod
-    def append_token_ids(self, token_ids: List[int]) -> None:
-        pass
-
-    @property
-    @abstractmethod
-    def block_id(self) -> Optional[int]:
-        pass
-
-    @block_id.setter
-    @abstractmethod
-    def block_id(self, value: Optional[int]) -> None:
-        """NOTE: Do not use this API outside Block."""
-        self._block_id = value
-
-    @property
-    @abstractmethod
-    def token_ids(self) -> List[int]:
-        pass
-
-    @property
-    @abstractmethod
-    def num_tokens_total(self) -> int:
-        """The number of tokens till the current block (inclusive)
-        """
-        pass
-
-    @property
-    @abstractmethod
-    def num_empty_slots(self) -> int:
-        pass
-
-    @property
-    @abstractmethod
-    def is_full(self) -> bool:
-        pass
-
-    @property
-    @abstractmethod
-    def prev_block(self) -> Optional["Block"]:
-        pass
-
-    @property
-    @abstractmethod
-    def extra_hash(self) -> Optional[int]:
-        return None
-
-    @property
-    @abstractmethod
-    def computed(self) -> bool:
-        raise NotImplementedError
-
-    @computed.setter
-    @abstractmethod
-    def computed(self, value) -> bool:
-        """Should be only used by PrefixCacingAllocator"""
-        raise NotImplementedError
-
-    @property
-    @abstractmethod
-    def last_accessed(self) -> float:
-        raise NotImplementedError
-
-    @last_accessed.setter
-    @abstractmethod
-    def last_accessed(self, last_accessed_ts: float):
-        raise NotImplementedError
-
-    class Factory(Protocol):
-
-        @abstractmethod
-        def __call__(
-            self,
-            prev_block: Optional["Block"],
-            token_ids: List[int],
-            block_size: int,
-            allocator: "BlockAllocator",
-            block_id: Optional[int] = None,
-            computed: bool = False,
-            extra_hash: Optional[int] = None,
-        ) -> "Block":
-            pass
-
-    @property
-    @abstractmethod
-    def content_hash(self) -> Optional[int]:
-        """Return the content-based hash of the current block, or None if it is
-        not yet defined or not supported.
-
-        For the content-based hash to be defined, the current block must be
-        full.
-        """
-        return None
-
-
-class BlockAllocator(ABC):
-
-    @abstractmethod
-    def allocate_mutable_block(self, prev_block: Optional[Block],
-                               extra_hash: Optional[int]) -> Block:
-        pass
-
-    @abstractmethod
-    def allocate_immutable_block(self, prev_block: Optional[Block],
-                                 token_ids: List[int],
-                                 extra_hash: Optional[int]) -> Block:
-        pass
-
-    @abstractmethod
-    def allocate_immutable_blocks(self, prev_block: Optional[Block],
-                                  block_token_ids: List[List[int]],
-                                  extra_hash: Optional[int]) -> List[Block]:
-        pass
-
-    @abstractmethod
-    def free(self, block: Block) -> None:
-        pass
-
-    @abstractmethod
-    def fork(self, last_block: Block) -> List[Block]:
-        pass
-
-    @abstractmethod
-    def get_num_total_blocks(self) -> int:
-        pass
-
-    @abstractmethod
-    def get_num_free_blocks(self) -> int:
-        pass
-
-    @abstractmethod
-    def get_physical_block_id(self, absolute_id: int) -> int:
-        pass
-
-    @abstractmethod
-    def swap_out(self, blocks: List[Block]) -> None:
-        pass
-
-    @abstractmethod
-    def swap_in(self, blocks: List[Block]) -> None:
-        pass
-
-    @property
-    @abstractmethod
-    def all_block_ids(self) -> FrozenSet[int]:
-        pass
-
-    @abstractmethod
-    def clear_copy_on_writes(self) -> List[Tuple[int, int]]:
-        pass
-
-    @abstractmethod
-    def mark_blocks_as_accessed(self, block_ids: List[int],
-                                now: float) -> None:
-        pass
-
-    @abstractmethod
-    def mark_blocks_as_computed(self, block_ids: List[int]) -> None:
-        pass
-
-    @abstractmethod
-    def get_common_computed_block_ids(
-            self, computed_seq_block_ids: List[List[int]]) -> List[int]:
-        pass
-
-    @abstractmethod
-    def cow_block_if_not_appendable(self, block: Block) -> BlockId:
-        """NOTE: This should not be used besides Block"""
-        pass
-
-    @abstractmethod
-    def promote_to_immutable_block(self, block: Block) -> BlockId:
-        """NOTE: This should not be used besides Block"""
-        pass
-
-    @abstractmethod
-    def get_num_full_blocks_touched(self, blocks: List[Block]) -> int:
-        pass
-
-    @abstractmethod
-    def get_prefix_cache_hit_rate(self) -> float:
-        """Prefix cache hit rate. -1 means not supported or disabled."""
-        pass
-
-    @abstractmethod
-    def reset_prefix_cache(self) -> bool:
-        """Reset prefix cache."""
-        pass
-
-    class NoFreeBlocksError(ValueError):
-        pass
-
-    @abstractmethod
-    def find_cached_blocks_prefix(
-        self,
-        block_hashes: List[int],
-    ) -> List[int]:
-        pass
-
-
-class DeviceAwareBlockAllocator(ABC):
-
-    @abstractmethod
-    def allocate_mutable_block(self,
-                               prev_block: Optional[Block],
-                               device: Device,
-                               extra_hash: Optional[int] = None) -> Block:
-        pass
-
-    @abstractmethod
-    def allocate_immutable_block(self,
-                                 prev_block: Optional[Block],
-                                 token_ids: List[int],
-                                 device: Device,
-                                 extra_hash: Optional[int] = None) -> Block:
-        pass
-
-    @abstractmethod
-    def allocate_immutable_blocks(
-        self,
-        prev_block: Optional[Block],
-        block_token_ids: List[List[int]],
-        device: Device,
-        extra_hash: Optional[int] = None,
-    ) -> List[Block]:
-        pass
-
-    @abstractmethod
-    def get_num_free_blocks(self, device: Device) -> int:
-        pass
-
-    @abstractmethod
-    def get_num_total_blocks(self, device: Device) -> int:
-        pass
-
-    @abstractmethod
-    def free(self, block: Block) -> None:
-        pass
-
-    @abstractmethod
-    def fork(self, last_block: Block) -> List[Block]:
-        pass
-
-    @property
-    @abstractmethod
-    def all_block_ids(self) -> FrozenSet[int]:
-        pass
-
-    @abstractmethod
-    def clear_copy_on_writes(self) -> List[Tuple[int, int]]:
-        pass
-
-    @abstractmethod
-    def mark_blocks_as_accessed(self, block_ids: List[int],
-                                now: float) -> None:
-        pass
-
-    @abstractmethod
-    def mark_blocks_as_computed(self, block_ids: List[int]) -> None:
-        pass
-
-    @abstractmethod
-    def get_common_computed_block_ids(
-            self, computed_seq_block_ids: List[List[int]]) -> List[int]:
-        pass
-
-    @abstractmethod
-    def get_num_full_blocks_touched(self, blocks: List[Block],
-                                    device: Device) -> int:
-        pass
-
-    @abstractmethod
-    def swap(self, blocks: List[Block], src_device: Device,
-             dst_device: Device) -> Dict[int, int]:
-        pass
-
-    @abstractmethod
-    def get_physical_block_id(self, device: Device, absolute_id: int) -> int:
-        pass
-
-    @abstractmethod
-    def allocate_or_get_null_block(self) -> Block:
-        """
-        Null blocks are used as a placeholders for KV cache blocks that have
-        been dropped due to sliding window.
-        There is at most one null block per allocator.
-        """
-        pass
-
-    @abstractmethod
-    def get_prefix_cache_hit_rate(self, device: Device) -> float:
-        """Prefix cache hit rate. -1 means not supported or disabled."""
-        pass
-
-    @abstractmethod
-    def reset_prefix_cache(self, device: Optional[Device] = None) -> bool:
-        """Reset prefix cache."""
-        pass
-
-    @abstractmethod
-    def find_cached_blocks_prefix(
-        self,
-        block_hashes: List[int],
-        device: Device = Device.GPU,
-    ) -> List[int]:
-        pass

vllm/core/block/naive_block.py

-# SPDX-License-Identifier: Apache-2.0
-# SPDX-FileCopyrightText: Copyright contributors to the vLLM project
-
-from collections import deque
-from typing import Deque, FrozenSet, Iterable, List, Optional, Tuple, Union
-
-from vllm.core.block.common import (BlockPool, CopyOnWriteTracker, RefCounter,
-                                    get_all_blocks_recursively)
-from vllm.core.block.interfaces import Block, BlockAllocator, BlockId, Device
-
-Refcount = int
-
-
-class NaiveBlockAllocator(BlockAllocator):
-    """A simple block allocator that manages blocks of memory without prefix
-    caching.
-
-    Args:
-        create_block (Block.Factory): A factory function for creating new
-            blocks. This is used when a NaiveBlockAllocator is composed within
-            a prefix caching allocator -- the naive block allocator must
-            construct prefix caching blocks (but shouldn't know anything else
-            about them).
-        num_blocks (int): The total number of blocks to manage.
-        block_size (int): The size of each block in tokens.
-        block_ids (Optional[Iterable[int]], optional): An optional iterable of
-            block IDs. If not provided, block IDs will be assigned sequentially
-            from 0 to num_blocks - 1.
-    """
-
-    def __init__(
-        self,
-        create_block: Block.Factory,
-        num_blocks: int,
-        block_size: int,
-        block_ids: Optional[Iterable[int]] = None,
-        block_pool: Optional[BlockPool] = None,
-    ):
-        if block_ids is None:
-            block_ids = range(num_blocks)
-
-        self._free_block_indices: Deque[BlockId] = deque(block_ids)
-        self._all_block_indices = frozenset(block_ids)
-        assert len(self._all_block_indices) == num_blocks
-
-        self._refcounter = RefCounter(
-            all_block_indices=self._free_block_indices)
-        self._block_size = block_size
-
-        self._cow_tracker = CopyOnWriteTracker(
-            refcounter=self._refcounter.as_readonly())
-
-        if block_pool is None:
-            extra_factor = 4
-            # Pre-allocate "num_blocks * extra_factor" block objects.
-            # The "* extra_factor" is a buffer to allow more block objects
-            # than physical blocks
-            self._block_pool = BlockPool(self._block_size, create_block, self,
-                                         num_blocks * extra_factor)
-        else:
-            # In this case, the block pool is provided by the caller,
-            # which means that there is most likely a need to share
-            # a block pool between allocators
-            self._block_pool = block_pool
-
-    def allocate_immutable_block(self,
-                                 prev_block: Optional[Block],
-                                 token_ids: List[int],
-                                 extra_hash: Optional[int] = None,
-                                 device: Optional[Device] = None) -> Block:
-        """Allocates a new immutable block with the given token IDs, linked to
-        the previous block.
-
-        Args:
-            prev_block (Optional[Block]): The previous block in the sequence. If
-                None, then the block to be allocated is the first block in the
-                sequence.
-            token_ids (List[int]): The token IDs to be stored in the new block.
-
-        Returns:
-            Block: The newly allocated immutable block.
-        """
-        assert device is None
-        block = self.allocate_mutable_block(prev_block=prev_block)
-        block.append_token_ids(token_ids)
-        return block
-
-    def allocate_immutable_blocks(
-            self,
-            prev_block: Optional[Block],
-            block_token_ids: List[List[int]],
-            extra_hash: Optional[int] = None,
-            device: Optional[Device] = None) -> List[Block]:
-        assert device is None
-        num_blocks = len(block_token_ids)
-
-        block_ids = []
-        for i in range(num_blocks):
-            block_ids.append(self._allocate_block_id())
-
-        blocks = []
-        for i in range(num_blocks):
-            prev_block = self._block_pool.init_block(
-                prev_block=prev_block,
-                token_ids=block_token_ids[i],
-                block_size=self._block_size,
-                physical_block_id=block_ids[i])
-            blocks.append(prev_block)
-
-        return blocks
-
-    def allocate_mutable_block(self,
-                               prev_block: Optional[Block],
-                               extra_hash: Optional[int] = None,
-                               device: Optional[Device] = None) -> Block:
-        """Allocates a new mutable block, linked to the previous block.
-
-        Args:
-            prev_block (Optional[Block]): The previous block in the sequence. If
-                None, then the block to be allocated is the first block in the
-                sequence.
-
-        Returns:
-            Block: The newly allocated mutable block.
-        """
-        assert device is None
-        block_id = self._allocate_block_id()
-        block = self._block_pool.init_block(prev_block=prev_block,
-                                            token_ids=[],
-                                            block_size=self._block_size,
-                                            physical_block_id=block_id)
-        return block
-
-    def _allocate_block_id(self) -> BlockId:
-        if not self._free_block_indices:
-            raise BlockAllocator.NoFreeBlocksError()
-
-        block_id = self._free_block_indices.popleft()
-        self._refcounter.incr(block_id)
-        return block_id
-
-    def _free_block_id(self, block: Union[Block, BlockId]) -> None:
-        if isinstance(block, Block):
-            block_id = block.block_id
-            block.block_id = None
-        else:
-            block_id = block
-        assert block_id is not None
-
-        refcount = self._refcounter.decr(block_id)
-        if refcount == 0:
-            self._free_block_indices.appendleft(block_id)
-
-    def free(self, block: Block, keep_block_object: bool = False) -> None:
-        # Release the physical block id
-        self._free_block_id(block)
-
-        # Release the block object
-        if not keep_block_object:
-            self._block_pool.free_block(block)
-
-    def free_block_id(self, block_id: BlockId) -> None:
-        self._free_block_id(block_id)
-
-    def fork(self, last_block: Block) -> List[Block]:
-        """Creates a new sequence of blocks that shares the same underlying
-        memory as the original sequence.
-
-        Args:
-            last_block (Block): The last block in the original sequence.
-
-        Returns:
-            List[Block]: The new sequence of blocks that shares the same memory
-                as the original sequence.
-        """
-        source_blocks = get_all_blocks_recursively(last_block)
-
-        forked_blocks: List[Block] = []
-        prev_block = None
-        for block in source_blocks:
-
-            # Increment refcount for each block.
-            assert block.block_id is not None
-            refcount = self._refcounter.incr(block.block_id)
-            assert refcount != 1, "can't fork freed block"
-
-            forked_block = self._block_pool.init_block(
-                prev_block=prev_block,
-                token_ids=block.token_ids,
-                block_size=self._block_size,
-                physical_block_id=block.block_id)
-
-            forked_blocks.append(forked_block)
-            prev_block = forked_blocks[-1]
-
-        return forked_blocks
-
-    def get_num_free_blocks(self) -> int:
-        return len(self._free_block_indices)
-
-    def get_num_total_blocks(self) -> int:
-        return len(self._all_block_indices)
-
-    def get_physical_block_id(self, absolute_id: int) -> int:
-        """Returns the zero-offset block id on certain block allocator
-        given the absolute block id.
-
-        Args:
-            absolute_id (int): The absolute block id for the block 
-                in whole allocator.
-
-        Returns:
-            int: The zero-offset block id on certain device.
-        """
-        return sorted(self._all_block_indices).index(absolute_id)
-
-    @property
-    def refcounter(self):
-        return self._refcounter
-
-    @property
-    def all_block_ids(self) -> FrozenSet[int]:
-        return self._all_block_indices
-
-    def cow_block_if_not_appendable(self, block: Block) -> BlockId:
-        """Performs a copy-on-write operation on the given block if it is not
-        appendable.
-
-        Args:
-            block (Block): The block to check for copy-on-write.
-
-        Returns:
-            BlockId: The block index of the new block if a copy-on-write 
-                operation was performed, or the original block index if
-                no copy-on-write was necessary.
-        """
-        src_block_id = block.block_id
-        assert src_block_id is not None
-
-        if self._cow_tracker.is_appendable(block):
-            return src_block_id
-
-        self._free_block_id(block)
-        trg_block_id = self._allocate_block_id()
-
-        self._cow_tracker.record_cow(src_block_id, trg_block_id)
-
-        return trg_block_id
-
-    def clear_copy_on_writes(self) -> List[Tuple[BlockId, BlockId]]:
-        """Returns the copy-on-write source->destination mapping and clears it.
-
-        Returns:
-            List[Tuple[BlockId, BlockId]]: A list mapping source
-                block indices to destination block indices.
-        """
-        return self._cow_tracker.clear_cows()
-
-    def mark_blocks_as_accessed(self, block_ids: List[int],
-                                now: float) -> None:
-        """Mark blocks as accessed, used in prefix caching.
-
-        Since the naive allocator does not implement prefix caching, we do
-        nothing.
-        """
-        pass
-
-    def mark_blocks_as_computed(self, block_ids: List[int]) -> None:
-        """Mark blocks as computed, used in prefix caching.
-
-        Since the naive allocator does not implement prefix caching, we do
-        nothing.
-        """
-        pass
-
-    def get_common_computed_block_ids(
-            self, computed_seq_block_ids: List[List[int]]) -> List[int]:
-        """Determine blocks that can be skipped in prefill.
-
-        Since the naive allocator does not support prefix caching, always return
-        an empty list.
-        """
-        return []
-
-    def promote_to_immutable_block(self, block: Block) -> BlockId:
-        raise NotImplementedError("There is no promotion for naive blocks")
-
-    def get_num_full_blocks_touched(self, blocks: List[Block]) -> int:
-        """Returns the number of full blocks that will be touched by
-        swapping in/out.
-
-        Args:
-            blocks: List of blocks to be swapped.
-        Returns:
-            int: the number of full blocks that will be touched by
-                swapping in/out the given blocks. Non full blocks are ignored
-                when deciding the number of blocks to touch.
-        """
-        # NOTE: for naive block, we use set to eliminate common blocks among
-        # seqs, also we compare the empty slots in the mutable blocks with
-        # lookahead slots to get the number of unique new block that are
-        # needed.
-        old_block_set = set()
-        for block in blocks:
-            if block.is_full:
-                old_block_set.add(block)
-        return len(old_block_set)
-
-    def swap_out(self, blocks: List[Block]) -> None:
-        for block in blocks:
-            self._free_block_id(block)
-
-    def swap_in(self, blocks: List[Block]) -> None:
-        for block in blocks:
-            # Here we allocate either immutable or mutable block and then
-            # extract its block_id. Note that the block object is released
-            # and the block_id is assigned to "block" to allow reusing the
-            # existing "block" object
-            if block.is_full:
-                tmp_block = self.allocate_immutable_block(
-                    prev_block=block.prev_block, token_ids=block.token_ids)
-            else:
-                tmp_block = self.allocate_mutable_block(
-                    prev_block=block.prev_block)
-                tmp_block.append_token_ids(block.token_ids)
-
-            block_id = tmp_block.block_id
-            tmp_block.block_id = None
-            self._block_pool.free_block(tmp_block)
-
-            block.block_id = block_id  # Assign block_id
-
-    def get_prefix_cache_hit_rate(self) -> float:
-        return -1
-
-    def reset_prefix_cache(self) -> bool:
-        """No prefix cache for naive block allocator."""
-        return True
-
-    def find_cached_blocks_prefix(self, block_hashes: List[int]) -> List[int]:
-        # Not applicable for naive block allocator.
-        return []
-
-
-class NaiveBlock(Block):
-    """An implementation of the Block class that does not support prefix
-    caching.
-
-    The NaiveBlock class represents a block of token IDs with a fixed size. It
-    provides methods for appending token IDs to the block and manages copy-on
-    -write operations when necessary.
-
-    Args:
-        prev_block (Block): The previous block in the sequence.
-        token_ids (List[int]): The initial token IDs to be stored in the block.
-        block_size (int): The maximum number of token IDs that can be stored in
-            the block.
-        allocator (BlockAllocator): The block allocator associated with this
-            block.
-        block_id (Optional[int], optional): The physical block index
-            of this block. Defaults to None, which means no allocation has been
-            made.
-        _cow_target (Optional[Block], optional): The copy-on-write target block.
-            If not provided, it defaults to self.
-    """
-
-    def __init__(self,
-                 prev_block: Optional[Block],
-                 token_ids: List[int],
-                 block_size: int,
-                 allocator: BlockAllocator,
-                 block_id: Optional[int] = None,
-                 _cow_target: Optional[Block] = None,
-                 extra_hash: Optional[int] = None):
-        self._token_ids: List[int] = []
-        self._block_size = block_size
-        self._prev_block = prev_block
-        self._block_id = block_id
-        self._allocator = allocator
-        self._cow_target = _cow_target if _cow_target is not None else self
-
-        self._append_token_ids_no_cow(token_ids)
-
-    def append_token_ids(self, token_ids: List[int]) -> None:
-        """Appends the given token IDs to the block and performs a 
-        copy-on-write if necessary.
-
-        Args:
-            token_ids (Optional[List[int]]): The token IDs to be appended 
-                to the block.
-        """
-        self._append_token_ids_no_cow(token_ids)
-
-        if self._block_id is not None:
-            self._block_id = (self._allocator.cow_block_if_not_appendable(
-                self._cow_target))
-
-    def _append_token_ids_no_cow(self, token_ids: List[int]) -> None:
-        """Appends the given token IDs to the block
-
-        Args:
-            token_ids (List[int]): The token IDs to be appended to the block.
-        """
-        if len(token_ids) == 0:
-            return
-
-        assert len(token_ids) <= self.num_empty_slots
-
-        self._token_ids.extend(token_ids)
-
-    @property
-    def computed(self) -> bool:
-        raise NotImplementedError
-
-    @computed.setter
-    def computed(self, value) -> None:
-        raise NotImplementedError
-
-    @property
-    def last_accessed(self) -> float:
-        raise NotImplementedError
-
-    @last_accessed.setter
-    def last_accessed(self, last_accessed_ts: float):
-        raise NotImplementedError
-
-    @property
-    def block_id(self) -> Optional[int]:
-        return self._block_id
-
-    @block_id.setter
-    def block_id(self, value: Optional[int]) -> None:
-        self._block_id = value
-
-    @property
-    def is_full(self) -> bool:
-        return self.num_empty_slots == 0
-
-    @property
-    def num_empty_slots(self) -> int:
-        return self._block_size - len(self.token_ids)
-
-    @property
-    def token_ids(self) -> List[int]:
-        return self._token_ids
-
-    @property
-    def num_tokens_total(self) -> int:
-        raise NotImplementedError(
-            "num_tokens_total is not used for naive block")
-
-    @property
-    def block_size(self) -> int:
-        return self._block_size
-
-    @property
-    def prev_block(self) -> Optional["Block"]:
-        return self._prev_block
-
-    @property
-    def extra_hash(self):
-        return None
-
-    @property
-    def content_hash(self) -> Optional[int]:
-        return None

vllm/core/block/prefix_caching_block.py

-# SPDX-License-Identifier: Apache-2.0
-# SPDX-FileCopyrightText: Copyright contributors to the vLLM project
-"""Token blocks."""
-import sys
-from bisect import bisect_left
-from os.path import commonprefix
-from typing import (Callable, Dict, FrozenSet, Iterable, List, Optional, Set,
-                    Tuple)
-
-from vllm.core.block.common import (CacheMetricData, CopyOnWriteTracker,
-                                    get_all_blocks_recursively)
-from vllm.core.block.interfaces import (Block, BlockAllocator, BlockId, Device,
-                                        DeviceAwareBlockAllocator)
-from vllm.core.block.naive_block import (BlockPool, NaiveBlock,
-                                         NaiveBlockAllocator)
-from vllm.core.evictor import EvictionPolicy, Evictor, make_evictor
-from vllm.logger import init_logger
-from vllm.sequence import Sequence
-
-PrefixHash = int
-
-# By default, we init our block access time as _DEFAULT_LAST_ACCESSED_TIME
-# so that if we find one block is still hold _DEFAULT_LAST_ACCESSED_TIME,
-# then we know this block hasn't been accessed yet.
-_DEFAULT_LAST_ACCESSED_TIME = -1
-
-logger = init_logger(__name__)
-
-
-class BlockTracker:
-    """Used to track the status of a block inside the prefix caching allocator
-    """
-    __slots__ = ("active", "last_accessed", "computed")
-
-    def reset(self):
-        self.last_accessed: float = _DEFAULT_LAST_ACCESSED_TIME
-        self.computed: bool = False
-
-    def __init__(self):
-        self.active: bool = False
-        self.reset()
-
-    def enable(self):
-        assert not self.active
-        self.active = True
-        self.reset()
-
-    def disable(self):
-        assert self.active
-        self.active = False
-        self.reset()
-
-
-class PrefixCachingBlockAllocator(BlockAllocator):
-    """A block allocator that implements prefix caching.
-
-    The PrefixCachingBlockAllocator maintains a cache of blocks based on their
-    content hash. It reuses blocks with the same content hash to avoid redundant
-    memory allocation. The allocator also supports copy-on-write operations.
-
-    Args:
-        num_blocks (int): The total number of blocks to manage.
-        block_size (int): The size of each block in tokens.
-        block_ids (Optional[Iterable[int]], optional): An optional iterable of
-            block IDs. If not provided, block IDs will be assigned sequentially
-            from 0 to num_blocks - 1.
-    """
-
-    # Note that we use 'None' as a string here instead of None because
-    # as of Python 3.12, hash(None) returns a constant predictable value.
-    # This could possibly make it easier to find and exploit hash
-    # collisions. 'None' as a string will be hashed differently per process,
-    # but consistently within the same process. This is the same as the
-    # behavior of None prior to Python 3.12.
-    _none_hash: int = hash('None')
-
-    # Implements Block.Factory.
-    def __init__(
-        self,
-        num_blocks: int,
-        block_size: int,
-        block_ids: Optional[Iterable[int]] = None,
-        eviction_policy: EvictionPolicy = EvictionPolicy.LRU,
-    ):
-        if block_ids is None:
-            block_ids = range(num_blocks)
-
-        self._block_size = block_size
-
-        # A mapping of prefix hash to block index. All blocks which have a
-        # prefix hash will be in this dict, even if they have refcount 0.
-        self._cached_blocks: Dict[PrefixHash, BlockId] = {}
-
-        # A list of immutable block IDs that have been touched by scheduler
-        # and should be marked as computed after an entire batch of sequences
-        # are scheduled.
-        self._touched_blocks: Set[BlockId] = set()
-
-        # Used to track status of each physical block id
-        self._block_tracker: Dict[BlockId, BlockTracker] = {}
-        for block_id in block_ids:
-            self._block_tracker[block_id] = BlockTracker()
-
-        # Pre-allocate "num_blocks * extra_factor" block objects.
-        # The "* extra_factor" is a buffer to allow more block objects
-        # than physical blocks
-        extra_factor = 4
-        self._block_pool = BlockPool(self._block_size, self._create_block,
-                                     self, num_blocks * extra_factor)
-
-        # An allocator for blocks that do not have prefix hashes.
-        self._hashless_allocator = NaiveBlockAllocator(
-            create_block=self._create_block,  # type: ignore
-            num_blocks=num_blocks,
-            block_size=block_size,
-            block_ids=block_ids,
-            block_pool=self._block_pool,  # Share block pool here
-        )
-
-        # Evitor used to maintain how we want to handle those computed blocks
-        # if we find memory pressure is high.
-        self.eviction_policy = eviction_policy
-        self.evictor: Evictor = make_evictor(self.eviction_policy)
-
-        # We share the refcounter between allocators. This allows us to promote
-        # blocks originally allocated in the hashless allocator to immutable
-        # blocks.
-        self._refcounter = self._hashless_allocator.refcounter
-
-        self._cow_tracker = CopyOnWriteTracker(
-            refcounter=self._refcounter.as_readonly())
-
-        self.metric_data = CacheMetricData()
-
-    def _create_block(
-        self,
-        prev_block: Optional[Block],
-        token_ids: List[int],
-        block_size: int,
-        allocator: BlockAllocator,
-        block_id: Optional[int] = None,
-        computed: bool = False,
-        extra_hash: Optional[int] = None,
-    ) -> Block:
-        # Bind block to self.
-        allocator = self
-
-        return PrefixCachingBlock(
-            prev_block=prev_block,
-            token_ids=token_ids,
-            block_size=block_size,
-            block_id=block_id,
-            allocator=allocator,
-            computed=computed,
-            extra_hash=extra_hash,
-        )
-
-    def allocate_immutable_block(self,
-                                 prev_block: Optional[Block],
-                                 token_ids: List[int],
-                                 extra_hash: Optional[int] = None,
-                                 device: Optional[Device] = None) -> Block:
-        """Allocates an immutable block with the given token IDs, reusing cached
-        blocks if possible.
-
-        Args:
-            prev_block (Optional[Block]): The previous block in the sequence.
-            token_ids (List[int]): The token IDs to be stored in the block.
-
-        Returns:
-            Block: The allocated immutable block.
-        """
-        assert device is None
-        assert_prefix_caching_block_or_none(prev_block)
-
-        # First, try to create a block that points to cached data
-        block = self._block_pool.init_block(prev_block=prev_block,
-                                            token_ids=token_ids,
-                                            block_size=self._block_size,
-                                            physical_block_id=None,
-                                            extra_hash=extra_hash)
-        assert block.content_hash is not None
-
-        cached_block_id = self._cached_blocks.get(block.content_hash, None)
-        if cached_block_id is not None:
-            self.metric_data.query(hit=True)
-            block.block_id = cached_block_id
-            self._incr_refcount_cached_block(block)
-            return block
-        self.metric_data.query(hit=False)
-        self._block_pool.free_block(block)
-
-        # No cached block => Allocate a new block
-        block = self.allocate_mutable_block(prev_block, extra_hash=extra_hash)
-        block.append_token_ids(token_ids)
-        return block
-
-    def allocate_immutable_blocks(
-            self,
-            prev_block: Optional[Block],
-            block_token_ids: List[List[int]],
-            extra_hash: Optional[int] = None,
-            device: Optional[Device] = None) -> List[Block]:
-        blocks = []
-        for token_ids in block_token_ids:
-            prev_block = self.allocate_immutable_block(prev_block=prev_block,
-                                                       token_ids=token_ids,
-                                                       device=device,
-                                                       extra_hash=extra_hash)
-            blocks.append(prev_block)
-        return blocks
-
-    def allocate_mutable_block(self,
-                               prev_block: Optional[Block],
-                               extra_hash: Optional[int] = None,
-                               device: Optional[Device] = None) -> Block:
-        """Allocates a mutable block. If there are no free blocks, this will
-        evict unused cached blocks.
-
-        Args:
-            prev_block (Block): The previous block in the sequence.
-                None is not allowed unlike it is super class.
-
-        Returns:
-            Block: The allocated mutable block.
-        """
-        assert device is None
-        assert_prefix_caching_block_or_none(prev_block)
-
-        block_id = self._allocate_block_id()
-        block = self._block_pool.init_block(prev_block=prev_block,
-                                            token_ids=[],
-                                            block_size=self._block_size,
-                                            physical_block_id=block_id,
-                                            extra_hash=extra_hash)
-        assert not block.computed
-        assert block.content_hash is None
-        return block
-
-    def _incr_refcount_cached_block(self, block: Block) -> None:
-        # Set this block to be "computed" since it is pointing to a
-        # cached block id (which was already computed)
-        block.computed = True
-
-        block_id = block.block_id
-        assert block_id is not None
-
-        refcount = self._refcounter.incr(block_id)
-        if refcount == 1:
-            # In case a cached block was evicted, restore its tracking
-            if block_id in self.evictor:
-                self.evictor.remove(block_id)
-
-            self._track_block_id(block_id, computed=True)
-
-    def _decr_refcount_cached_block(self, block: Block) -> None:
-        # Ensure this is immutable/cached block
-        assert block.content_hash is not None
-
-        block_id = block.block_id
-        assert block_id is not None
-
-        refcount = self._refcounter.decr(block_id)
-        if refcount > 0:
-            block.block_id = None
-            return
-        else:
-            assert refcount == 0
-
-        # No longer used
-        assert block.content_hash in self._cached_blocks
-
-        # Add the cached block to the evictor
-        # (This keeps the cached block around so it can be reused)
-        self.evictor.add(block_id, block.content_hash, block.num_tokens_total,
-                         self._block_tracker[block_id].last_accessed)
-
-        # Stop tracking the block
-        self._untrack_block_id(block_id)
-
-        block.block_id = None
-
-    def _decr_refcount_hashless_block(self, block: Block) -> None:
-        block_id = block.block_id
-        assert block_id is not None
-
-        # We may have a fork case where block is shared,
-        # in which case, we cannot remove it from tracking
-        refcount = self._refcounter.get(block_id)
-        if refcount == 1:
-            self._untrack_block_id(block_id)
-
-        # Decrement refcount of the block_id, but do not free the block object
-        # itself (will be handled by the caller)
-        self._hashless_allocator.free(block, keep_block_object=True)
-
-    def _allocate_block_id(self) -> BlockId:
-        """First tries to allocate a block id from the hashless allocator,
-        and if there are no blocks, then tries to evict an unused cached block.
-        """
-        hashless_block_id = self._maybe_allocate_hashless_block_id()
-        if hashless_block_id is not None:
-            return hashless_block_id
-
-        evicted_block_id = self._maybe_allocate_evicted_block_id()
-        if evicted_block_id is not None:
-            return evicted_block_id
-
-        # No block available in hashless allocator, nor in unused cache blocks.
-        raise BlockAllocator.NoFreeBlocksError()
-
-    def _maybe_allocate_hashless_block_id(self) -> Optional[BlockId]:
-        try:
-            # Allocate mutable block and extract its block_id
-            block = self._hashless_allocator.allocate_mutable_block(
-                prev_block=None)
-            block_id = block.block_id
-            self._block_pool.free_block(block)
-
-            self._track_block_id(block_id, computed=False)
-            return block_id
-        except BlockAllocator.NoFreeBlocksError:
-            return None
-
-    def _maybe_allocate_evicted_block_id(self) -> Optional[BlockId]:
-        if self.evictor.num_blocks == 0:
-            return None
-
-        # Here we get an evicted block, which is only added
-        # into evictor if its ref counter is 0
-        # and since its content would be changed, we need
-        # to remove it from _cached_blocks's tracking list
-        block_id, content_hash_to_evict = self.evictor.evict()
-
-        # Sanity checks
-        assert content_hash_to_evict in self._cached_blocks
-        _block_id = self._cached_blocks[content_hash_to_evict]
-        assert self._refcounter.get(_block_id) == 0
-        assert _block_id == block_id
-
-        self._cached_blocks.pop(content_hash_to_evict)
-
-        self._refcounter.incr(block_id)
-        self._track_block_id(block_id, computed=False)
-
-        return block_id
-
-    def _free_block_id(self, block: Block) -> None:
-        """Decrements the refcount of the block. The block may be in two 
-        possible states: (1) immutable/cached or (2) mutable/hashless. 
-        In the first case, the refcount is decremented directly and the block
-        may be possibly added to the evictor. In other case, hashless 
-        allocator free(..) with keep_block_object=True is called to only free
-        the block id (since the block object may be reused by the caller)
-        """
-        block_id = block.block_id
-        assert block_id is not None, "Freeing unallocated block is undefined"
-
-        if block.content_hash is not None:
-            # Immutable: This type of block is always cached, and we want to
-            # keep it in the evictor for future reuse
-            self._decr_refcount_cached_block(block)
-        else:
-            # Mutable: This type of block is not cached, so we release it
-            # directly to the hashless allocator
-            self._decr_refcount_hashless_block(block)
-
-        assert block.block_id is None
-
-    def free(self, block: Block, keep_block_object: bool = False) -> None:
-        """Release the block (look at free_block_id(..) docs)
-        """
-        # Release the physical block index
-        self._free_block_id(block)
-
-        # Release the block object to the pool
-        if not keep_block_object:
-            self._block_pool.free_block(block)
-
-    def fork(self, last_block: Block) -> List[Block]:
-        """Creates a new sequence of blocks that shares the same underlying
-        memory as the original sequence.
-
-        Args:
-            last_block (Block): The last block in the original sequence.
-
-        Returns:
-            List[Block]: The new sequence of blocks that shares the same memory
-                as the original sequence.
-        """
-        source_blocks = get_all_blocks_recursively(last_block)
-
-        forked_blocks: List[Block] = []
-        prev_block = None
-        for block in source_blocks:
-            block_id = block.block_id
-            assert block_id is not None
-
-            refcount = self._refcounter.incr(block_id)
-            assert refcount != 1, "can't fork free'd block_id = {}".format(
-                block_id)
-
-            forked_block = self._block_pool.init_block(
-                prev_block=prev_block,
-                token_ids=block.token_ids,
-                block_size=self._block_size,
-                physical_block_id=block_id,
-                extra_hash=block.extra_hash)
-
-            forked_blocks.append(forked_block)
-            prev_block = forked_blocks[-1]
-
-        return forked_blocks
-
-    def get_num_free_blocks(self, device: Optional[Device] = None) -> int:
-        assert device is None
-        # The number of free blocks is the number of hashless free blocks
-        # plus the number of blocks evictor could free from its list.
-        return self._hashless_allocator.get_num_free_blocks(
-        ) + self.evictor.num_blocks
-
-    def get_num_total_blocks(self) -> int:
-        return self._hashless_allocator.get_num_total_blocks()
-
-    def get_physical_block_id(self, absolute_id: int) -> int:
-        """Returns the zero-offset block id on certain block allocator
-        given the absolute block id.
-
-        Args:
-            absolute_id (int): The absolute block id for the block 
-                in whole allocator.
-
-        Returns:
-            int: The rzero-offset block id on certain device.
-        """
-        return sorted(self.all_block_ids).index(absolute_id)
-
-    @property
-    def all_block_ids(self) -> FrozenSet[int]:
-        return self._hashless_allocator.all_block_ids
-
-    def get_prefix_cache_hit_rate(self) -> float:
-        return self.metric_data.get_hit_rate()
-
-    def reset_prefix_cache(self) -> bool:
-        """Reset prefix cache. This function may be used in RLHF
-        flows to invalid prefix caching after the weights are updated,
-        or used for resetting prefix caching status for benchmarking.
-
-        Returns:
-            bool: True if the prefix cache is successfully reset,
-            False otherwise.
-        """
-        num_used_blocks = (self.get_num_total_blocks() -
-                           self.get_num_free_blocks())
-        if num_used_blocks > 0:
-            logger.warning(
-                "Failed to reset prefix cache because some "
-                "blocks (%d) are not freed yet", num_used_blocks)
-            return False
-
-        # Free all blocks in the evictor.
-        while (block_id :=
-               self._maybe_allocate_evicted_block_id()) is not None:
-            self._hashless_allocator.free_block_id(block_id)
-
-        # Should not have any cached blocks because all blocks are evicted.
-        assert not self._cached_blocks
-
-        # Reset the evictor.
-        self.evictor = make_evictor(self.eviction_policy)
-
-        # Reset the block tracker.
-        for block_id in self._block_tracker:
-            self._block_tracker[block_id] = BlockTracker()
-
-        # Reset the metrics.
-        self.metric_data = CacheMetricData()
-
-        logger.info("Successfully reset prefix cache")
-        return True
-
-    def is_block_cached(self, block: Block) -> bool:
-        assert block.content_hash is not None
-        return block.content_hash in self._cached_blocks
-
-    def promote_to_immutable_block(self, block: Block) -> BlockId:
-        """Once a mutable block is full, it can be promoted to an immutable
-        block. This means that its content can be referenced by future blocks
-        having the same prefix.
-
-        Note that if we already have a cached block with the same content, we
-        will replace the newly-promoted block's mapping with the existing cached
-        block id.
-
-        Args:
-            block: The mutable block to be promoted.
-
-        Returns:
-            BlockId: Either the original block index, or the block index of
-                the previously cached block matching the same content.
-        """
-        # Ensure block can be promoted
-        assert block.content_hash is not None
-        assert block.block_id is not None
-        assert self._refcounter.get(block.block_id) > 0
-
-        if block.content_hash not in self._cached_blocks:
-            # No cached content hash => Set this block as cached.
-            # Note that this block cannot be marked as computed yet
-            # because other sequences in the same batch cannot reuse
-            # this block.
-            self._cached_blocks[block.content_hash] = block.block_id
-            # Mark this block as touched so that it can be marked as
-            # computed after the entire batch of sequences are scheduled.
-            self._touched_blocks.add(block.block_id)
-            return block.block_id
-
-        # Reuse the cached content hash
-        self._decr_refcount_hashless_block(block)
-        block.block_id = self._cached_blocks[block.content_hash]
-
-        # Increment refcount of the cached block and (possibly) restore
-        # it from the evictor.
-        # Note that in this case, the block is marked as computed
-        self._incr_refcount_cached_block(block)
-
-        return block.block_id
-
-    def cow_block_if_not_appendable(self, block: Block) -> BlockId:
-        """Performs a copy-on-write operation on the given block if it is not
-        appendable.
-
-        Args:
-            block (Block): The block to check for copy-on-write.
-
-        Returns:
-            BlockId: The block index of the new block if a copy-on-write 
-                operation was performed, or the original block index if
-                no copy-on-write was necessary.
-        """
-        src_block_id = block.block_id
-        assert src_block_id is not None
-
-        if self._cow_tracker.is_appendable(block):
-            return src_block_id
-
-        self._free_block_id(block)
-        trg_block_id = self._allocate_block_id()
-
-        self._cow_tracker.record_cow(src_block_id, trg_block_id)
-
-        return trg_block_id
-
-    def clear_copy_on_writes(self) -> List[Tuple[BlockId, BlockId]]:
-        """Returns the copy-on-write source->destination mapping and clears it.
-
-        Returns:
-            List[Tuple[BlockId, BlockId]]: A list mapping source
-                block indices to destination block indices.
-        """
-        return self._cow_tracker.clear_cows()
-
-    def mark_blocks_as_accessed(self, block_ids: List[int],
-                                now: float) -> None:
-        """Mark blocks as accessed, used in prefix caching.
-
-        If the block is added into evictor, we need to update corresponding
-        info in evictor's metadata.
-        """
-
-        for block_id in block_ids:
-            if self._block_tracker[block_id].active:
-                self._block_tracker[block_id].last_accessed = now
-            elif block_id in self.evictor:
-                self.evictor.update(block_id, now)
-            else:
-                raise ValueError(
-                    "Mark block as accessed which is not belonged to GPU")
-
-    def mark_blocks_as_computed(self, block_ids: List[int]) -> None:
-        # Mark all touched blocks as computed.
-        for block_id in self._touched_blocks:
-            self._block_tracker[block_id].computed = True
-        self._touched_blocks.clear()
-
-    def _track_block_id(self, block_id: Optional[BlockId],
-                        computed: bool) -> None:
-        assert block_id is not None
-        self._block_tracker[block_id].enable()
-        self._block_tracker[block_id].computed = computed
-
-    def _untrack_block_id(self, block_id: Optional[BlockId]) -> None:
-        assert block_id is not None
-        self._block_tracker[block_id].disable()
-
-    def block_is_computed(self, block_id: int) -> bool:
-        if self._block_tracker[block_id].active:
-            return self._block_tracker[block_id].computed
-        else:
-            return block_id in self.evictor
-
-    def get_common_computed_block_ids(
-            self, computed_seq_block_ids: List[List[int]]) -> List[int]:
-        """Return the block ids that are common for a given sequence group.
-
-        Only those blocks that are immutable and already be marked
-        compyted would be taken consideration.
-        """
-
-        # NOTE We exclude the last block to avoid the case where the entire
-        # prompt is cached. This would cause erroneous behavior in model
-        # runner.
-
-        # It returns a list of int although type annotation says list of string.
-        if len(computed_seq_block_ids) == 1:
-            return computed_seq_block_ids[0]
-
-        return commonprefix([
-            ids for ids in computed_seq_block_ids  # type: ignore
-            if ids
-        ])
-
-    def get_num_full_blocks_touched(self, blocks: List[Block]) -> int:
-        """Returns the number of full blocks that will be touched by
-        swapping in/out.
-
-        Args:
-            blocks: List of blocks to be swapped.
-        Returns:
-            int: the number of full blocks that will be touched by
-                swapping in/out the given blocks. Non full blocks are ignored
-                when deciding the number of blocks to touch.
-        """
-        num_touched_blocks: int = 0
-        for block in blocks:
-            # If the block has a match in the cache and the cached
-            # block is not referenced, then we still count it as a
-            # touched block
-            if block.is_full and (not self.is_block_cached(block) or \
-                (block.content_hash is not None and \
-                self._cached_blocks[block.content_hash] in \
-                        self.evictor)):
-                num_touched_blocks += 1
-        return num_touched_blocks
-
-    def swap_out(self, blocks: List[Block]) -> None:
-        """Execute the swap out actions. Basically just free the 
-        given blocks.
-
-        Args:
-            blocks: List of blocks to be swapped out.
-        """
-        for block in blocks:
-            self._free_block_id(block)
-
-    def swap_in(self, blocks: List[Block]) -> None:
-        """Execute the swap in actions. Change the block id from 
-        old allocator to current allocator for each block to finish 
-        the block table update. 
-
-        Args:
-            blocks: List of blocks to be swapped in.
-        """
-        for block in blocks:
-            # Here we allocate either immutable or mutable block and then
-            # extract its block_id. Note that the block object is released
-            # and the block_id is assigned to "block" to allow reusing the
-            # existing "block" object
-            if block.is_full:
-                tmp_block = self.allocate_immutable_block(
-                    prev_block=block.prev_block,
-                    token_ids=block.token_ids,
-                    extra_hash=block.extra_hash)
-            else:
-                tmp_block = self.allocate_mutable_block(
-                    prev_block=block.prev_block, extra_hash=block.extra_hash)
-                tmp_block.append_token_ids(block.token_ids)
-
-            block_id = tmp_block.block_id
-            self._block_pool.free_block(tmp_block)
-
-            block.block_id = block_id  # Assign block_id
-
-    def find_cached_blocks_prefix(self, block_hashes: List[int]) -> List[int]:
-        """
-        Given a list of block hashes, return the prefix of the block hashes that
-        are all cached.
-
-        Since a block's block hash includes the hashes of all previous blocks,
-        and we only allocate/deallocate blocks in the entire sequence, so if a
-        block is cached, then all previous blocks are also cached. With this
-        property, we can use binary search to find the prefix of cached blocks.
-
-        Args:
-            block_hashes (List[int]): The list of block hashes.
-
-        Returns:
-            List[int]: The prefix of the `block_hashes` that are cached.
-        """
-
-        def _block_is_cached(block_hash: PrefixHash) -> bool:
-            if block_hash not in self._cached_blocks:
-                return False
-
-            cached_block_id = self._cached_blocks[block_hash]
-            # We only consider the blocks that are marked as computed.
-            return self.block_is_computed(cached_block_id)
-
-        def _bisect_left(a, x, key: Callable[[PrefixHash], bool]) -> int:
-
-            # python <= 3.10 don't have the key argument
-            if sys.version_info < (3, 10):
-                a = [key(e) for e in a]
-                return bisect_left(a, x)
-            else:
-                return bisect_left(a, x, key=key)
-
-        # Look for the first block that's not cached, and returns the prefix
-        # i.e. blocks that are cached.
-        idx = _bisect_left(block_hashes,
-                           True,
-                           key=lambda x: not _block_is_cached(x))
-        return block_hashes[:idx]
-
-
-class PrefixCachingBlock(Block):
-    """A block implementation that supports prefix caching.
-
-    The PrefixCachingBlock class represents a block of token IDs with prefix
-    caching capabilities. It wraps a NaiveBlock internally and provides
-    additional functionality for content hashing and promoting immutable blocks
-    with the prefix caching allocator.
-
-    Args:
-        prev_block (Optional[PrefixCachingBlock]): The previous block in the
-            sequence.
-        token_ids (List[int]): The initial token IDs to be stored in the block.
-        block_size (int): The maximum number of token IDs that can be stored in
-            the block.
-        allocator (BlockAllocator): The prefix
-            caching block allocator associated with this block.
-        block_id (Optional[int], optional): The physical block index
-            of this block. Defaults to None.
-        extra_hash (Optional[int]): The hash value of additional factors
-            such as adapters that influence the block, apart from the token_ids.
-    """
-
-    # Note that we use 'None' as a string here instead of None because
-    # as of Python 3.12, hash(None) returns a constant predictable value.
-    # This could possibly make it easier to find and exploit hash
-    # collisions. 'None' as a string will be hashed differently per process,
-    # but consistently within the same process. This is the same as the
-    # behavior of None prior to Python 3.12.
-    _none_hash: int = hash('None')
-
-    def __init__(
-        self,
-        prev_block: Optional[Block],
-        token_ids: List[int],
-        block_size: int,
-        allocator: BlockAllocator,
-        block_id: Optional[int] = None,
-        computed: bool = False,
-        extra_hash: Optional[int] = None,
-    ):
-        assert isinstance(allocator, PrefixCachingBlockAllocator), (
-            "Currently this class is only tested with "
-            "PrefixCachingBlockAllocator. Got instead allocator = {}".format(
-                allocator))
-        assert_prefix_caching_block_or_none(prev_block)
-
-        self._prev_block = prev_block
-        self._cached_content_hash: Optional[int] = None
-        self._cached_num_tokens_total: int = 0
-        self._allocator = allocator
-        self._last_accessed: float = _DEFAULT_LAST_ACCESSED_TIME
-        self._computed = computed
-        self._extra_hash = extra_hash
-
-        # On the first time, we create the block object, and next we only
-        # reinitialize it
-        if hasattr(self, "_block"):
-            self._block.__init__(  # type: ignore[has-type]
-                prev_block=prev_block,
-                token_ids=token_ids,
-                block_size=block_size,
-                block_id=block_id,
-                allocator=self._allocator)
-        else:
-            self._block = NaiveBlock(prev_block=prev_block,
-                                     token_ids=token_ids,
-                                     block_size=block_size,
-                                     block_id=block_id,
-                                     allocator=self._allocator)
-
-        self._update_num_tokens_total()
-
-    def _update_num_tokens_total(self):
-        """Incrementally computes the number of tokens that there is
-        till the current block (included)
-        """
-        res = 0
-
-        # Add all previous blocks
-        if self._prev_block is not None:
-            res += self._prev_block.num_tokens_total
-
-        # Add current block
-        res += len(self.token_ids)
-
-        self._cached_num_tokens_total = res
-
-    @property
-    def computed(self) -> bool:
-        return self._computed
-
-    @computed.setter
-    def computed(self, value) -> None:
-        self._computed = value
-
-    @property
-    def last_accessed(self) -> float:
-        return self._last_accessed
-
-    @last_accessed.setter
-    def last_accessed(self, last_accessed_ts: float):
-        self._last_accessed = last_accessed_ts
-
-    def append_token_ids(self, token_ids: List[int]) -> None:
-        """Appends the given token IDs to the block and registers the block as
-        immutable if the block becomes full.
-
-        Args:
-            token_ids (List[int]): The token IDs to be appended to the block.
-        """
-        # Ensure this is mutable block (not promoted)
-        assert self.content_hash is None
-        assert not self.computed
-
-        if len(token_ids) == 0:
-            return
-
-        # Ensure there are input tokens
-        assert token_ids, "Got token_ids = {}".format(token_ids)
-
-        # Naive block handles CoW.
-        self._block.append_token_ids(token_ids)
-        self._update_num_tokens_total()
-
-        # If the content hash is present, then the block can be made immutable.
-        # Register ourselves with the allocator, potentially replacing the
-        # physical block index.
-        if self.content_hash is not None:
-            self.block_id = self._allocator.promote_to_immutable_block(self)
-
-    @property
-    def block_id(self) -> Optional[int]:
-        return self._block.block_id
-
-    @block_id.setter
-    def block_id(self, value) -> None:
-        self._block.block_id = value
-
-    @property
-    def is_full(self) -> bool:
-        return self._block.is_full
-
-    @property
-    def num_empty_slots(self) -> int:
-        return self._block.num_empty_slots
-
-    @property
-    def num_tokens_total(self) -> int:
-        return self._cached_num_tokens_total
-
-    @property
-    def block_size(self) -> int:
-        return self._block.block_size
-
-    @property
-    def token_ids(self) -> List[int]:
-        return self._block.token_ids
-
-    @property
-    def prev_block(self) -> Optional[Block]:
-        return self._prev_block
-
-    @property
-    def extra_hash(self) -> Optional[int]:
-        return self._extra_hash
-
-    @property
-    def content_hash(self) -> Optional[int]:
-        """Return the content-based hash of the current block, or None if it is
-        not yet defined.
-
-        For the content-based hash to be defined, the current block must be
-        full.
-        """
-        # If the hash is already computed, return it.
-        if self._cached_content_hash is not None:
-            return self._cached_content_hash
-
-        # We cannot compute a hash for the current block because it is not full.
-        if not self.is_full:
-            return None
-
-        is_first_block = self._prev_block is None
-        prev_block_hash = (
-            self._none_hash if is_first_block else
-            self._prev_block.content_hash  # type: ignore
-        )
-
-        # Previous block exists but does not yet have a hash.
-        # Return no hash in this case.
-        if prev_block_hash == self._none_hash and not is_first_block:
-            return None
-
-        self._cached_content_hash = PrefixCachingBlock.hash_block_tokens(
-            is_first_block,
-            prev_block_hash,
-            cur_block_token_ids=self.token_ids,
-            extra_hash=self._extra_hash)
-        return self._cached_content_hash
-
-    @classmethod
-    def hash_block_tokens(cls,
-                          is_first_block: bool,
-                          prev_block_hash: Optional[int],
-                          cur_block_token_ids: List[int],
-                          extra_hash: Optional[int] = None) -> int:
-        """Computes a hash value corresponding to the contents of a block and
-        the contents of the preceding block(s). The hash value is used for
-        prefix caching.
-
-        Parameters:
-        - is_first_block (bool): A flag indicating if the block is the first in
-            the sequence.
-        - prev_block_hash (Optional[int]): The hash of the previous block. None
-            if this is the first block.
-        - cur_block_token_ids (List[int]): A list of token ids in the current
-            block. The current block is assumed to be full.
-        - extra_hash (Optional[int]): The hash value of additional factors
-            such as adapters that influence the block, apart from the token_ids.
-
-        Returns:
-        - int: The computed hash value for the block.
-        """
-        if is_first_block and prev_block_hash is None:
-            prev_block_hash = cls._none_hash
-        return hash((is_first_block, prev_block_hash, *cur_block_token_ids,
-                     extra_hash))
-
-
-class ComputedBlocksTracker:
-    """
-    Tracks the computed blocks for each sequence.
-
-    Internally, it maintains a map from sequence id to the list of block hashes
-    for the sequence. We cache the hashes of the full blocks for each sequence,
-    and make sure the hash is calculated in the same way as the allocator.
-    When a sequence is being decoded, we also update the sequence's hash
-    accordingly and incrementally.
-
-    From the sequence hash, with prefix caching enabled, we could also calculate
-    the number of cached tokens for the sequence by looking up the number of
-    cached block hashes in the allocator.
-    """
-
-    # Note that we use 'None' as a string here instead of None because
-    # as of Python 3.12, hash(None) returns a constant predictable value.
-    # This could possibly make it easier to find and exploit hash
-    # collisions. 'None' as a string will be hashed differently per process,
-    # but consistently within the same process. This is the same as the
-    # behavior of None prior to Python 3.12.
-    _none_hash: int = hash('None')
-
-    def __init__(
-        self,
-        allocator: DeviceAwareBlockAllocator,
-        block_size: int,
-        enable_caching: bool,
-    ):
-        self._allocator = allocator
-        self._block_size = block_size
-        self._enable_caching = enable_caching
-
-        # A map from seq_id to the list of block hashes for the
-        # sequence. This is so that we don't have to recompute the block hashes
-        # for the sequence when we need to check if the sequence is cached.
-        # Note a block that's not full will not have its hash calculated and
-        # recorded.
-        self._seq_id_to_blocks_hashes: Dict[int, List[int]] = {}
-
-        # A map from seq_id to the number of tokens that are cached for the
-        # sequence.
-        # We need this so that a sequence in continuous prefill doesn't
-        # accidentally see its cached token count change. See comments in
-        # `get_num_cached_tokens` for more details.
-        self._seq_id_to_num_tokens_computed: Dict[int, int] = {}
-
-    def _update_seq_hashes(self, seq: Sequence) -> None:
-        """Incrementally update the sequence's block hashes and record them."""
-        assert self._enable_caching
-
-        block_hashes_recorded = self._seq_id_to_blocks_hashes.get(
-            seq.seq_id, [])
-        cur_num_blocks_recorded = len(block_hashes_recorded)
-        token_ids = seq.get_token_ids()
-        assert len(token_ids) >= cur_num_blocks_recorded * self._block_size, (
-            f"The sequence has {len(token_ids)} tokens, but"
-            f" already recorded {cur_num_blocks_recorded} blocks. "
-            "This should not happen since we assume blocks are "
-            "only appended other than recomputation. When the sequence is "
-            "recomputed, we should have removed the info of the old blocks.")
-        # Update the computed block hashes for the sequence. Since only full
-        # blocks are considered as "computed", we take floor here.
-        num_computed_blocks = len(token_ids) // self._block_size
-
-        # We need to know the hash of the previous block to compute the hash of
-        # the current block so that blocks could be uniquely identified across
-        # sequences of prefixes.
-        prev_block_hash = (self._none_hash if cur_num_blocks_recorded == 0 else
-                           block_hashes_recorded[-1])
-        # Only update the computed block hashes for the new blocks
-        for i in range(cur_num_blocks_recorded, num_computed_blocks):
-            assert len(token_ids) >= (i + 1) * self._block_size
-            block_token_ids = token_ids[i * self._block_size:(i + 1) *
-                                        self._block_size]
-
-            # NOTE: If there are any factors affecting the block besides
-            # token_ids, they should be added as input to extra_hash.
-            extra_hash = seq.extra_hash()
-
-            # This has to be kept in sync with the allocator's hash
-            # calculation.
-            block_hash = PrefixCachingBlock.hash_block_tokens(
-                is_first_block=prev_block_hash == self._none_hash,
-                prev_block_hash=prev_block_hash,
-                cur_block_token_ids=block_token_ids,
-                extra_hash=extra_hash,
-            )
-            block_hashes_recorded.append(block_hash)
-            prev_block_hash = block_hash
-
-        self._seq_id_to_blocks_hashes[seq.seq_id] = block_hashes_recorded
-
-    def get_num_cached_tokens(self, seq: Sequence) -> int:
-        if not self._enable_caching:
-            return 0
-
-        # We always try to update the sequence hashes on the fly.
-        # This is to ensure that we don't miss any cached tokens for the
-        # sequence during decode.
-        # This routine should only update hash for any new blocks too.
-        self._update_seq_hashes(seq)
-
-        num_computed_tokens_prev = self._seq_id_to_num_tokens_computed.get(
-            seq.seq_id, None)
-
-        # TODO(rickyx): This hack could be removed once we mark blocks as
-        # computed correctly with chunked prefills.
-        if num_computed_tokens_prev is not None and seq.is_prefill():
-            # For a sequence that is still in prefill, we don't
-            # recompute the number of cached tokens.
-            # This also handles correctly chunked prefill since currently
-            # we mark blocks as computed even if the sequence is still partially
-            # prefilled. So a continuously prefilled sequence should not
-            # see its cached token count change while running.
-            return num_computed_tokens_prev
-
-        block_hashes = self._seq_id_to_blocks_hashes[seq.seq_id]
-
-        # This is O(logN), where N is the number of blocks.
-        num_cached_blocks = len(
-            self._allocator.find_cached_blocks_prefix(block_hashes))
-        num_cached_tokens = num_cached_blocks * self._block_size
-        self._seq_id_to_num_tokens_computed[seq.seq_id] = num_cached_tokens
-        return num_cached_tokens
-
-    def remove_seq(self, seq_id: int) -> None:
-        """Stop tracking the sequence."""
-        if not self._enable_caching:
-            return
-        assert seq_id in self._seq_id_to_blocks_hashes
-        del self._seq_id_to_blocks_hashes[seq_id]
-
-        assert seq_id in self._seq_id_to_num_tokens_computed
-        del self._seq_id_to_num_tokens_computed[seq_id]
-
-
-class LastAccessBlocksTracker:
-    """Manages the last access time of the tracked sequences, in order to allow
-    an efficient update of allocator's block last access times
-    """
-
-    def __init__(self, allocator):
-        self._allocator = allocator
-        self._seq_last_access: Dict[int, Optional[float]] = {}
-
-    def add_seq(self, seq_id: int) -> None:
-        """Start tracking seq_id
-        """
-        assert seq_id not in self._seq_last_access
-        self._seq_last_access[seq_id] = None
-
-    def remove_seq(self, seq_id: int) -> None:
-        """Stop tracking seq_id
-        """
-        assert seq_id in self._seq_last_access
-        del self._seq_last_access[seq_id]
-
-    def update_last_access(self, seq_id: int, time: float) -> None:
-        assert seq_id in self._seq_last_access
-        self._seq_last_access[seq_id] = time
-
-    def update_seq_blocks_last_access(self, seq_id: int,
-                                      block_ids: List[int]) -> None:
-        assert seq_id in self._seq_last_access
-
-        ts = self._seq_last_access[seq_id]
-
-        if ts is None:
-            # No last access was recorded, no need to update.
-            return
-
-        self._allocator.mark_blocks_as_accessed(block_ids, ts)
-
-
-def assert_prefix_caching_block_or_none(block: Optional[Block]):
-    if block is None:
-        return
-    assert isinstance(block,
-                      PrefixCachingBlock), "Got block = {}".format(block)

vllm/core/block/utils.py

-# SPDX-License-Identifier: Apache-2.0
-# SPDX-FileCopyrightText: Copyright contributors to the vLLM project
-"""Block manager utils."""
-from vllm.sequence import SequenceGroup
-from vllm.utils import (STR_NOT_IMPL_ENC_DEC_PREFIX_CACHE,
-                        STR_NOT_IMPL_ENC_DEC_SWA)
-
-
-def check_no_caching_or_swa_for_blockmgr_encdec(
-        block_mgr, seq_group: SequenceGroup) -> None:
-    '''
-    Enforce that prefix caching & sliding-window attention (SWA)
-    are currently unsupported *specifically* for encoder/decoder models.
-
-    Raises NotImplementedError if unsupported scenario is detected.
-
-    Arguments:
-
-    * block_mgr: BlockSpaceManager instance
-    * seq_group: SequenceGroup passed to block_mgr
-    '''
-
-    if seq_group.is_encoder_decoder():
-        if block_mgr.max_block_sliding_window is not None:
-            raise NotImplementedError(STR_NOT_IMPL_ENC_DEC_SWA)
-
-        if block_mgr.enable_caching:
-            raise NotImplementedError(STR_NOT_IMPL_ENC_DEC_PREFIX_CACHE)

vllm/core/block_manager.py

-# SPDX-License-Identifier: Apache-2.0
-# SPDX-FileCopyrightText: Copyright contributors to the vLLM project
-"""A block manager that manages token blocks."""
-from typing import Dict, List, Optional
-from typing import Sequence as GenericSequence
-from typing import Tuple
-
-from vllm.core.block.block_table import BlockTable
-from vllm.core.block.cpu_gpu_block_allocator import CpuGpuBlockAllocator
-from vllm.core.block.interfaces import Block
-from vllm.core.block.prefix_caching_block import (ComputedBlocksTracker,
-                                                  LastAccessBlocksTracker)
-from vllm.core.block.utils import check_no_caching_or_swa_for_blockmgr_encdec
-from vllm.core.interfaces import AllocStatus, BlockSpaceManager
-from vllm.sequence import Sequence, SequenceGroup, SequenceStatus
-from vllm.utils import Device
-
-SeqId = int
-EncoderSeqId = str
-
-
-class SelfAttnBlockSpaceManager(BlockSpaceManager):
-    """BlockSpaceManager which manages the allocation of KV cache.
-
-    It owns responsibility for allocation, swapping, allocating memory for
-    autoregressively-generated tokens, and other advanced features such as
-    prefix caching, forking/copy-on-write, and sliding-window memory allocation.
-
-    This class implements the design described in
-    https://github.com/vllm-project/vllm/pull/3492.
-
-    Lookahead slots
-        The block manager has the notion of a "lookahead slot". These are slots
-        in the KV cache that are allocated for a sequence. Unlike the other
-        allocated slots, the content of these slots is undefined -- the worker
-        may use the memory allocations in any way.
-
-        In practice, a worker could use these lookahead slots to run multiple
-        forward passes for a single scheduler invocation. Each successive
-        forward pass would write KV activations to the corresponding lookahead
-        slot. This allows low inter-token latency use-cases, where the overhead
-        of continuous batching scheduling is amortized over >1 generated tokens.
-
-        Speculative decoding uses lookahead slots to store KV activations of
-        proposal tokens.
-
-        See https://github.com/vllm-project/vllm/pull/3250 for more information
-        on lookahead scheduling.
-
-    Args:
-        block_size (int): The size of each memory block.
-        num_gpu_blocks (int): The number of memory blocks allocated on GPU.
-        num_cpu_blocks (int): The number of memory blocks allocated on CPU.
-        watermark (float, optional): The threshold used for memory swapping.
-            Defaults to 0.01.
-        sliding_window (Optional[int], optional): The size of the sliding
-            window. Defaults to None.
-        enable_caching (bool, optional): Flag indicating whether caching is
-            enabled. Defaults to False.
-    """
-
-    def __init__(
-        self,
-        block_size: int,
-        num_gpu_blocks: int,
-        num_cpu_blocks: int,
-        watermark: float = 0.01,
-        sliding_window: Optional[int] = None,
-        enable_caching: bool = False,
-    ) -> None:
-        self.block_size = block_size
-        self.num_total_gpu_blocks = num_gpu_blocks
-        self.num_total_cpu_blocks = num_cpu_blocks
-
-        self.sliding_window = sliding_window
-        # max_block_sliding_window is the max number of blocks that need to be
-        # allocated
-        self.max_block_sliding_window = None
-        if sliding_window is not None:
-            # +1 here because // rounds down
-            num_blocks = sliding_window // block_size + 1
-            # +1 here because the last block may not be full,
-            # and so the sequence stretches one more block at the beginning
-            # For example, if sliding_window is 3 and block_size is 4,
-            # we may need 2 blocks when the second block only holds 1 token.
-            self.max_block_sliding_window = num_blocks + 1
-
-        self.watermark = watermark
-        assert watermark >= 0.0
-
-        self.enable_caching = enable_caching
-
-        self.watermark_blocks = int(watermark * num_gpu_blocks)
-
-        self.block_allocator = CpuGpuBlockAllocator.create(
-            allocator_type="prefix_caching" if enable_caching else "naive",
-            num_gpu_blocks=num_gpu_blocks,
-            num_cpu_blocks=num_cpu_blocks,
-            block_size=block_size,
-        )
-
-        self.block_tables: Dict[SeqId, BlockTable] = {}
-        self.cross_block_tables: Dict[EncoderSeqId, BlockTable] = {}
-
-        self._computed_blocks_tracker = ComputedBlocksTracker(
-            self.block_allocator, self.block_size, self.enable_caching)
-        self._last_access_blocks_tracker = LastAccessBlocksTracker(
-            self.block_allocator)
-
-    def can_allocate(self,
-                     seq_group: SequenceGroup,
-                     num_lookahead_slots: int = 0) -> AllocStatus:
-        # FIXME(woosuk): Here we assume that all sequences in the group share
-        # the same prompt. This may not be true for preempted sequences.
-
-        check_no_caching_or_swa_for_blockmgr_encdec(self, seq_group)
-
-        seq = seq_group.get_seqs(status=SequenceStatus.WAITING)[0]
-        num_required_blocks = BlockTable.get_num_required_blocks(
-            seq.get_token_ids(),
-            block_size=self.block_size,
-            num_lookahead_slots=num_lookahead_slots,
-        )
-
-        if seq_group.is_encoder_decoder():
-            encoder_seq = seq_group.get_encoder_seq()
-            assert encoder_seq is not None
-            num_required_blocks += BlockTable.get_num_required_blocks(
-                encoder_seq.get_token_ids(),
-                block_size=self.block_size,
-            )
-
-        if self.max_block_sliding_window is not None:
-            num_required_blocks = min(num_required_blocks,
-                                      self.max_block_sliding_window)
-
-        num_free_gpu_blocks = self.block_allocator.get_num_free_blocks(
-            device=Device.GPU)
-
-        # Use watermark to avoid frequent cache eviction.
-        if (self.num_total_gpu_blocks - num_required_blocks
-                < self.watermark_blocks):
-            return AllocStatus.NEVER
-        if num_free_gpu_blocks - num_required_blocks >= self.watermark_blocks:
-            return AllocStatus.OK
-        else:
-            return AllocStatus.LATER
-
-    def _allocate_sequence(self, seq: Sequence) -> BlockTable:
-        block_table = BlockTable(
-            block_size=self.block_size,
-            block_allocator=self.block_allocator,
-            max_block_sliding_window=self.max_block_sliding_window,
-        )
-        if seq.get_token_ids():
-            # NOTE: If there are any factors affecting the block besides
-            # token_ids, they should be added as input to extra_hash.
-            extra_hash = seq.extra_hash()
-
-            # Add blocks to the block table only if the sequence is non empty.
-            block_table.allocate(token_ids=seq.get_token_ids(),
-                                 extra_hash=extra_hash)
-
-        return block_table
-
-    def allocate(self, seq_group: SequenceGroup) -> None:
-
-        # Allocate self-attention block tables for decoder sequences
-        waiting_seqs = seq_group.get_seqs(status=SequenceStatus.WAITING)
-        assert not (set(seq.seq_id for seq in waiting_seqs)
-                    & self.block_tables.keys()), "block table already exists"
-
-        # NOTE: Here we assume that all sequences in the group have the same
-        # prompt.
-        seq = waiting_seqs[0]
-        block_table: BlockTable = self._allocate_sequence(seq)
-        self.block_tables[seq.seq_id] = block_table
-
-        # Track seq
-        self._last_access_blocks_tracker.add_seq(seq.seq_id)
-
-        # Assign the block table for each sequence.
-        for seq in waiting_seqs[1:]:
-            self.block_tables[seq.seq_id] = block_table.fork()
-
-            # Track seq
-            self._last_access_blocks_tracker.add_seq(seq.seq_id)
-
-        # Allocate cross-attention block table for encoder sequence
-        #
-        # NOTE: Here we assume that all sequences in the group have the same
-        # encoder prompt.
-        request_id = seq_group.request_id
-
-        assert (request_id
-                not in self.cross_block_tables), \
-            "block table already exists"
-
-        check_no_caching_or_swa_for_blockmgr_encdec(self, seq_group)
-
-        if seq_group.is_encoder_decoder():
-            encoder_seq = seq_group.get_encoder_seq()
-            assert encoder_seq is not None
-            block_table = self._allocate_sequence(encoder_seq)
-            self.cross_block_tables[request_id] = block_table
-
-    def can_append_slots(self, seq_group: SequenceGroup,
-                         num_lookahead_slots: int) -> bool:
-        """Determine if there is enough space in the GPU KV cache to continue
-        generation of the specified sequence group.
-
-        We use a worst-case heuristic: assume each touched block will require a
-        new allocation (either via CoW or new block). We can append slots if the
-        number of touched blocks is less than the number of free blocks.
-
-        "Lookahead slots" are slots that are allocated in addition to the slots
-        for known tokens. The contents of the lookahead slots are not defined.
-        This is used by speculative decoding when speculating future tokens.
-        """
-
-        num_touched_blocks = 0
-        for seq in seq_group.get_seqs(status=SequenceStatus.RUNNING):
-            block_table = self.block_tables[seq.seq_id]
-
-            num_touched_blocks += (
-                block_table.get_num_blocks_touched_by_append_slots(
-                    token_ids=block_table.get_unseen_token_ids(
-                        seq.get_token_ids()),
-                    num_lookahead_slots=num_lookahead_slots,
-                ))
-
-        num_free_gpu_blocks = self.block_allocator.get_num_free_blocks(
-            Device.GPU)
-        return num_touched_blocks <= num_free_gpu_blocks
-
-    def append_slots(
-        self,
-        seq: Sequence,
-        num_lookahead_slots: int,
-    ) -> List[Tuple[int, int]]:
-
-        block_table = self.block_tables[seq.seq_id]
-
-        block_table.append_token_ids(
-            token_ids=block_table.get_unseen_token_ids(seq.get_token_ids()),
-            num_lookahead_slots=num_lookahead_slots,
-            num_computed_slots=seq.data.get_num_computed_tokens(),
-            extra_hash=seq.extra_hash(),
-        )
-        # Return any new copy-on-writes.
-        new_cows = self.block_allocator.clear_copy_on_writes()
-        return new_cows
-
-    def free(self, seq: Sequence) -> None:
-        seq_id = seq.seq_id
-
-        if seq_id not in self.block_tables:
-            # Already freed or haven't been scheduled yet.
-            return
-
-        # Update seq block ids with the latest access time
-        self._last_access_blocks_tracker.update_seq_blocks_last_access(
-            seq_id, self.block_tables[seq.seq_id].physical_block_ids)
-
-        # Untrack seq
-        self._last_access_blocks_tracker.remove_seq(seq_id)
-        self._computed_blocks_tracker.remove_seq(seq_id)
-
-        # Free table/blocks
-        self.block_tables[seq_id].free()
-        del self.block_tables[seq_id]
-
-    def remove_seq_from_computed_blocks_tracker(self, seq: Sequence) -> None:
-        seq_id = seq.seq_id
-        self._computed_blocks_tracker.remove_seq(seq_id)
-
-    def free_cross(self, seq_group: SequenceGroup) -> None:
-        request_id = seq_group.request_id
-        if request_id not in self.cross_block_tables:
-            # Already freed or hasn't been scheduled yet.
-            return
-        self.cross_block_tables[request_id].free()
-        del self.cross_block_tables[request_id]
-
-    def get_block_table(self, seq: Sequence) -> List[int]:
-        block_ids = self.block_tables[seq.seq_id].physical_block_ids
-        return block_ids  # type: ignore
-
-    def get_cross_block_table(self, seq_group: SequenceGroup) -> List[int]:
-        request_id = seq_group.request_id
-        assert request_id in self.cross_block_tables
-        block_ids = self.cross_block_tables[request_id].physical_block_ids
-        assert all(b is not None for b in block_ids)
-        return block_ids  # type: ignore
-
-    def access_all_blocks_in_seq(self, seq: Sequence, now: float):
-        if self.enable_caching:
-            # Record the latest access time for the sequence. The actual update
-            # of the block ids is deferred to the sequence free(..) call, since
-            # only during freeing of block ids, the blocks are actually added to
-            # the evictor (which is when the most updated time is required)
-            # (This avoids expensive calls to mark_blocks_as_accessed(..))
-            self._last_access_blocks_tracker.update_last_access(
-                seq.seq_id, now)
-
-    def mark_blocks_as_computed(self, seq_group: SequenceGroup,
-                                token_chunk_size: int):
-        # If prefix caching is enabled, mark immutable blocks as computed
-        # right after they have been scheduled (for prefill). This assumes
-        # the scheduler is synchronous so blocks are actually computed when
-        # scheduling the next batch.
-        self.block_allocator.mark_blocks_as_computed([])
-
-    def get_common_computed_block_ids(
-            self, seqs: List[Sequence]) -> GenericSequence[int]:
-        """Determine which blocks for which we skip prefill.
-
-        With prefix caching we can skip prefill for previously-generated blocks.
-        Currently, the attention implementation only supports skipping cached
-        blocks if they are a contiguous prefix of cached blocks.
-
-        This method determines which blocks can be safely skipped for all
-        sequences in the sequence group.
-        """
-        computed_seq_block_ids = []
-        for seq in seqs:
-            all_blocks = self.block_tables[seq.seq_id].physical_block_ids
-            num_cached_tokens = (
-                self._computed_blocks_tracker.get_num_cached_tokens(seq))
-            assert num_cached_tokens % self.block_size == 0
-            num_cached_blocks = num_cached_tokens // self.block_size
-            computed_block_ids = all_blocks[:num_cached_blocks]
-            computed_seq_block_ids.append(computed_block_ids)
-
-        # NOTE(sang): This assumes seq_block_ids doesn't contain any None.
-        return self.block_allocator.get_common_computed_block_ids(
-            computed_seq_block_ids)  # type: ignore
-
-    def fork(self, parent_seq: Sequence, child_seq: Sequence) -> None:
-        if parent_seq.seq_id not in self.block_tables:
-            # Parent sequence has either been freed or never existed.
-            return
-        src_block_table = self.block_tables[parent_seq.seq_id]
-        self.block_tables[child_seq.seq_id] = src_block_table.fork()
-
-        # Track child seq
-        self._last_access_blocks_tracker.add_seq(child_seq.seq_id)
-
-    def can_swap_in(self, seq_group: SequenceGroup,
-                    num_lookahead_slots: int) -> AllocStatus:
-        """Returns the AllocStatus for the given sequence_group 
-        with num_lookahead_slots.
-
-        Args:
-            seq_group (SequenceGroup): The sequence group to swap in.
-            num_lookahead_slots (int): Number of lookahead slots used in 
-                speculative decoding, default to 0.
-
-        Returns:
-            AllocStatus: The AllocStatus for the given sequence group.
-        """
-        return self._can_swap(seq_group, Device.GPU, SequenceStatus.SWAPPED,
-                              num_lookahead_slots)
-
-    def swap_in(self, seq_group: SequenceGroup) -> List[Tuple[int, int]]:
-        """Returns the block id mapping (from CPU to GPU) generated by
-        swapping in the given seq_group with num_lookahead_slots.
-
-        Args:
-            seq_group (SequenceGroup): The sequence group to swap in.
-
-        Returns:
-            List[Tuple[int, int]]: The mapping of swapping block from CPU 
-                to GPU.
-        """
-        physical_block_id_mapping = []
-        for seq in seq_group.get_seqs(status=SequenceStatus.SWAPPED):
-            blocks = self.block_tables[seq.seq_id].blocks
-            if len(blocks) == 0:
-                continue
-
-            seq_swap_mapping = self.block_allocator.swap(blocks=blocks,
-                                                         src_device=Device.CPU,
-                                                         dst_device=Device.GPU)
-
-            # Refresh the block ids of the table (post-swap)
-            self.block_tables[seq.seq_id].update(blocks)
-
-            seq_physical_block_id_mapping = {
-                self.block_allocator.get_physical_block_id(
-                    Device.CPU, cpu_block_id):
-                self.block_allocator.get_physical_block_id(
-                    Device.GPU, gpu_block_id)
-                for cpu_block_id, gpu_block_id in seq_swap_mapping.items()
-            }
-
-            physical_block_id_mapping.extend(
-                list(seq_physical_block_id_mapping.items()))
-
-        return physical_block_id_mapping
-
-    def can_swap_out(self, seq_group: SequenceGroup) -> bool:
-        """Returns whether we can swap out the given sequence_group 
-        with num_lookahead_slots.
-
-        Args:
-            seq_group (SequenceGroup): The sequence group to swap out.
-
-        Returns:
-            bool: Whether it's possible to swap out current sequence group.
-        """
-        alloc_status = self._can_swap(seq_group, Device.CPU,
-                                      SequenceStatus.RUNNING)
-        return alloc_status == AllocStatus.OK
-
-    def swap_out(self, seq_group: SequenceGroup) -> List[Tuple[int, int]]:
-        """Returns the block id mapping (from GPU to CPU) generated by
-        swapping out the given sequence_group with num_lookahead_slots.
-
-        Args:
-            seq_group (SequenceGroup): The sequence group to swap out.
-
-        Returns:
-            List[Tuple[int, int]]: The mapping of swapping block from 
-                GPU to CPU.
-        """
-        physical_block_id_mapping = []
-        for seq in seq_group.get_seqs(status=SequenceStatus.RUNNING):
-            blocks = self.block_tables[seq.seq_id].blocks
-            if len(blocks) == 0:
-                continue
-
-            seq_swap_mapping = self.block_allocator.swap(blocks=blocks,
-                                                         src_device=Device.GPU,
-                                                         dst_device=Device.CPU)
-
-            # Refresh the block ids of the table (post-swap)
-            self.block_tables[seq.seq_id].update(blocks)
-
-            seq_physical_block_id_mapping = {
-                self.block_allocator.get_physical_block_id(
-                    Device.GPU, gpu_block_id):
-                self.block_allocator.get_physical_block_id(
-                    Device.CPU, cpu_block_id)
-                for gpu_block_id, cpu_block_id in seq_swap_mapping.items()
-            }
-
-            physical_block_id_mapping.extend(
-                list(seq_physical_block_id_mapping.items()))
-
-        return physical_block_id_mapping
-
-    def get_num_free_gpu_blocks(self) -> int:
-        return self.block_allocator.get_num_free_blocks(Device.GPU)
-
-    def get_num_free_cpu_blocks(self) -> int:
-        return self.block_allocator.get_num_free_blocks(Device.CPU)
-
-    def get_prefix_cache_hit_rate(self, device: Device) -> float:
-        return self.block_allocator.get_prefix_cache_hit_rate(device)
-
-    def reset_prefix_cache(self, device: Optional[Device] = None) -> bool:
-        return self.block_allocator.reset_prefix_cache(device)
-
-    def _can_swap(self,
-                  seq_group: SequenceGroup,
-                  device: Device,
-                  status: SequenceStatus,
-                  num_lookahead_slots: int = 0) -> AllocStatus:
-        """Returns the AllocStatus for swapping in/out the given sequence_group 
-        on to the 'device'.
-
-        Args:
-            seq_group (SequenceGroup): The sequence group to swap in/out.
-            device (Device): device to swap the 'seq_group' on.
-            status (SequenceStatus): The status of sequence which is needed
-                for action. RUNNING for swap out and SWAPPED for swap in
-            num_lookahead_slots (int): Number of lookahead slots used in 
-                speculative decoding, default to 0.
-
-        Returns:
-            AllocStatus: The AllocStatus for swapping in/out the given 
-                sequence_group on to the 'device'.
-        """
-        # First determine the number of blocks that will be touched by this
-        # swap. Then verify if there are available blocks in the device
-        # to perform the swap.
-        num_blocks_touched = 0
-        blocks: List[Block] = []
-        for seq in seq_group.get_seqs(status=status):
-            block_table = self.block_tables[seq.seq_id]
-            if block_table.blocks is not None:
-                # Compute the number blocks to touch for the tokens to be
-                # appended. This does NOT include the full blocks that need
-                # to be touched for the swap.
-                num_blocks_touched += \
-                    block_table.get_num_blocks_touched_by_append_slots(
-                        block_table.get_unseen_token_ids(seq.get_token_ids()),
-                        num_lookahead_slots=num_lookahead_slots)
-                blocks.extend(block_table.blocks)
-        # Compute the number of full blocks to touch and add it to the
-        # existing count of blocks to touch.
-        num_blocks_touched += self.block_allocator.get_num_full_blocks_touched(
-            blocks, device=device)
-
-        watermark_blocks = 0
-        if device == Device.GPU:
-            watermark_blocks = self.watermark_blocks
-
-        if self.block_allocator.get_num_total_blocks(
-                device) < num_blocks_touched:
-            return AllocStatus.NEVER
-        elif self.block_allocator.get_num_free_blocks(
-                device) - num_blocks_touched >= watermark_blocks:
-            return AllocStatus.OK
-        else:
-            return AllocStatus.LATER
-
-    def get_num_cached_tokens(self, seq: Sequence) -> int:
-        """Get the number of tokens in blocks that are already computed and
-        cached in the block manager for the sequence.
-        """
-        return self._computed_blocks_tracker.get_num_cached_tokens(seq)