[V1] Prefix caching for vision language models (#11187)

Signed-off-by: Cody Yu <hao.yu.cody@gmail.com>

tests/v1/core/test_prefix_caching.py

@@ -2,16 +2,23 @@
 import pytest
 
 from vllm.inputs import token_inputs
+from vllm.multimodal.inputs import PlaceholderRange
 from vllm.sampling_params import SamplingParams
 from vllm.utils import cdiv
 from vllm.v1.core.kv_cache_manager import KVCacheManager, Request
 from vllm.v1.core.kv_cache_utils import KVCacheBlock, hash_block_tokens
 
 
-def make_request(request_id, prompt_token_ids):
+def make_request(request_id,
+                 prompt_token_ids,
+                 mm_positions=None,
+                 mm_hashes=None):
     return Request(
         request_id=request_id,
-        inputs=token_inputs(prompt_token_ids=prompt_token_ids),
+        inputs=token_inputs(prompt_token_ids=prompt_token_ids,
+                            multi_modal_placeholders={"image": mm_positions}
+                            if mm_positions else None,
+                            multi_modal_hashes=mm_hashes),
         sampling_params=SamplingParams(max_tokens=17),
         eos_token_id=100,
         arrival_time=0,
@@ -38,6 +45,7 @@ def test_prefill():
     all_token_ids = common_token_ids + unique_token_ids
     req0 = make_request("0", all_token_ids)
     computed_blocks = manager.get_computed_blocks(req0)
+    assert len(req0.kv_block_hashes) == 3
     assert not computed_blocks
     blocks = manager.allocate_slots(req0, 55, computed_blocks)
     assert [b.block_id for b in blocks] == [0, 1, 2, 3, 4]
@@ -61,6 +69,7 @@ def test_prefill():
     unique_token_ids = [3] * 5
     req1 = make_request("1", common_token_ids + unique_token_ids)
     computed_blocks = manager.get_computed_blocks(req1)
+    assert len(req1.kv_block_hashes) == 3
     assert [b.block_id for b in computed_blocks] == [0, 1, 2]
     num_new_tokens = 53 - 3 * 16
     blocks = manager.allocate_slots(req1, num_new_tokens, computed_blocks)
@@ -90,6 +99,7 @@ def test_prefill():
     unique_token_ids = [3] * 6
     req2 = make_request("2", common_token_ids + unique_token_ids)
     computed_block = manager.get_computed_blocks(req2)
+    assert len(req2.kv_block_hashes) == 3
     assert [b.block_id for b in computed_block] == [0, 1, 2]
     num_new_tokens = 53 - 3 * 16
     blocks = manager.allocate_slots(req2, num_new_tokens, computed_blocks)
@@ -416,3 +426,77 @@ def test_cache_blocks():
     )
     assert len(manager.cached_block_hash_to_block) == 3
     assert blocks[0].block_hash is not None
+
+
+def test_mm_prefix_caching():
+    """
+    This tests that the multi-modal prefix caching is correct.
+    """
+    manager = KVCacheManager(
+        block_size=16,
+        num_gpu_blocks=10,
+        max_model_len=8192,
+        sliding_window=None,
+        enable_caching=True,
+        num_preallocate_tokens=16,
+    )
+
+    # Common prompt tokens (T is text tokens and P is image placeholder tokens)
+    # [T,...,T, P0,...,P0], [P0,...,P0,T,...,T,P1,...,P1], [P1,...,P1]
+    common_token_ids = list(range(10)) + [-1] * 6
+    common_token_ids += [-1] * 4 + list(range(10, 20)) + [-1] * 2
+    common_token_ids += [-1] * 16
+
+    common_mm_positions = [
+        PlaceholderRange(offset=11, length=10),
+        PlaceholderRange(offset=30, length=18),
+    ]
+    common_mm_hashes = ["aaa", "bbb"]
+
+    # A unique image plus some text tokens.
+    unique_token_ids = [-1] * 7 + [100] * 4
+    all_token_ids = common_token_ids + unique_token_ids
+    mm_positions = common_mm_positions + [
+        PlaceholderRange(offset=48, length=7)
+    ]
+    mm_hashes = common_mm_hashes + ["ccc"]
+    req0 = make_request("0",
+                        all_token_ids,
+                        mm_positions=mm_positions,
+                        mm_hashes=mm_hashes)
+    computed_blocks = manager.get_computed_blocks(req0)
+
+    # Completed block should have hashes with extra keys.
+    assert not computed_blocks
+    assert len(req0.kv_block_hashes) == 3
+    assert req0.kv_block_hashes[0].extra_keys == (("aaa", 0), )
+    assert req0.kv_block_hashes[1].extra_keys == (("aaa", 5), ("bbb", 0))
+    assert req0.kv_block_hashes[2].extra_keys == (("bbb", 2), )
+
+    blocks = manager.allocate_slots(req0, 59, computed_blocks)
+    assert [b.block_id for b in blocks] == [0, 1, 2, 3, 4]
+    req0.num_computed_tokens = 59
+
+    # Append slots without allocating a new block.
+    for _ in range(5):
+        req0.append_output_token_ids(8)
+    new_blocks = manager.append_slots(req0, 5)
+    assert new_blocks is not None and len(new_blocks) == 0
+
+    # The just completed block should have hashes with extra keys.
+    assert len(req0.kv_block_hashes) == 4
+    assert req0.kv_block_hashes[3].extra_keys == (("ccc", 0), )
+
+    # Cache hit.
+    unique_token_ids = [-1] * 7 + [200] * 5
+    all_token_ids = common_token_ids + unique_token_ids
+    mm_positions = common_mm_positions + [
+        PlaceholderRange(offset=48, length=7)
+    ]
+    mm_hashes = common_mm_hashes + ["ccc"]
+    req1 = make_request("1",
+                        all_token_ids,
+                        mm_positions=mm_positions,
+                        mm_hashes=mm_hashes)
+    computed_blocks = manager.get_computed_blocks(req1)
+    assert len(computed_blocks) == 3

tests/v1/engine/test_engine_args.py

@@ -31,14 +31,6 @@ def test_prefix_caching_from_cli():
     assert engine_args.enable_prefix_caching
 
 
-def test_defaults():
-    engine_args = EngineArgs(model="facebook/opt-125m")
-
-    # Assert V1 defaults
-    assert (engine_args.enable_prefix_caching
-            ), "V1 turns on prefix caching by default"
-
-
 def test_defaults_with_usage_context():
     engine_args = EngineArgs(model="facebook/opt-125m")
     vllm_config: VllmConfig = engine_args.create_engine_config(
@@ -52,10 +44,3 @@ def test_defaults_with_usage_context():
         UsageContext.OPENAI_API_SERVER)
     assert vllm_config.scheduler_config.max_num_seqs == 1024
     assert vllm_config.scheduler_config.max_num_batched_tokens == 2048
-
-
-def test_prefix_cache_disabled_with_multimodel():
-    engine_args = EngineArgs(model="llava-hf/llava-1.5-7b-hf")
-
-    vllm_config = engine_args.create_engine_config(UsageContext.LLM_CLASS)
-    assert not vllm_config.cache_config.enable_prefix_caching

vllm/engine/arg_utils.py

@@ -205,6 +205,7 @@ class EngineArgs:
         # by user.
         if self.enable_prefix_caching is None:
             self.enable_prefix_caching = bool(envs.VLLM_USE_V1)
+
         # Override max_num_seqs if it's not set by user.
         if self.max_num_seqs is None:
             self.max_num_seqs = 256 if not envs.VLLM_USE_V1 else 1024
@@ -1026,11 +1027,11 @@ class EngineArgs:
         device_config = DeviceConfig(device=self.device)
         model_config = self.create_model_config()
 
-        if model_config.is_multimodal_model:
-            if self.enable_prefix_caching:
-                logger.warning(
-                    "--enable-prefix-caching is currently not "
-                    "supported for multimodal models and has been disabled.")
+        if (model_config.is_multimodal_model and not envs.VLLM_USE_V1
+                and self.enable_prefix_caching):
+            logger.warning("--enable-prefix-caching is currently not "
+                           "supported for multimodal models in v0 and "
+                           "has been disabled.")
             self.enable_prefix_caching = False
 
         cache_config = CacheConfig(
@@ -1249,11 +1250,14 @@ class EngineArgs:
         # When no user override, set the default values based on the usage
         # context.
         # TODO(woosuk): Tune the default values for different hardware.
-        if self.max_num_batched_tokens is None:
-            if usage_context == UsageContext.LLM_CLASS:
-                self.max_num_batched_tokens = 8192
-            elif usage_context == UsageContext.OPENAI_API_SERVER:
-                self.max_num_batched_tokens = 2048
+        default_max_num_batched_tokens = {
+            UsageContext.LLM_CLASS: 8192,
+            UsageContext.OPENAI_API_SERVER: 2048,
+        }
+        if (self.max_num_batched_tokens is None
+                and usage_context in default_max_num_batched_tokens):
+            self.max_num_batched_tokens = default_max_num_batched_tokens[
+                usage_context]
             logger.warning(
                 "Setting max_num_batched_tokens to %d for %s usage context.",
                 self.max_num_batched_tokens, usage_context.value)
@@ -1263,9 +1267,6 @@ class EngineArgs:
         Override the EngineConfig's configs based on the usage context for V1.
         """
         assert envs.VLLM_USE_V1, "V1 is not enabled"
-        if engine_config.model_config.is_multimodal_model:
-            # TODO (ywang96): Enable APC by default when VLM supports it.
-            assert not engine_config.cache_config.enable_prefix_caching
 
 
 @dataclass

vllm/inputs/data.py

@@ -162,6 +162,11 @@ class TokenInputs(TypedDict):
     Placeholder ranges for the multi-modal data.
     """
 
+    multi_modal_hashes: NotRequired[List[str]]
+    """
+    The hashes of the multi-modal data.
+    """
+
     mm_processor_kwargs: NotRequired[Dict[str, Any]]
     """
     Optional multi-modal processor kwargs to be forwarded to the
@@ -177,6 +182,7 @@ def token_inputs(
     prompt: Optional[str] = None,
     multi_modal_data: Optional["MultiModalDataDict"] = None,
     multi_modal_inputs: Optional["MultiModalKwargs"] = None,
+    multi_modal_hashes: Optional[List[str]] = None,
     multi_modal_placeholders: Optional["MultiModalPlaceholderDict"] = None,
     mm_processor_kwargs: Optional[Dict[str, Any]] = None,
 ) -> TokenInputs:
@@ -191,6 +197,8 @@ def token_inputs(
         inputs["multi_modal_data"] = multi_modal_data
     if multi_modal_inputs is not None:
         inputs["multi_modal_inputs"] = multi_modal_inputs
+    if multi_modal_hashes is not None:
+        inputs["multi_modal_hashes"] = multi_modal_hashes
     if multi_modal_placeholders is not None:
         inputs["multi_modal_placeholders"] = multi_modal_placeholders
     if mm_processor_kwargs is not None:
@@ -295,6 +303,18 @@ class SingletonInputsAdapter:
 
         assert_never(inputs)
 
+    @cached_property
+    def multi_modal_hashes(self) -> List[str]:
+        inputs = self.inputs
+
+        if inputs["type"] == "token":
+            return inputs.get("multi_modal_hashes", [])
+
+        if inputs["type"] == "multimodal":
+            return inputs.get("mm_hashes", [])
+
+        assert_never(inputs)
+
     @cached_property
     def multi_modal_placeholders(self) -> "MultiModalPlaceholderDict":
         inputs = self.inputs

vllm/multimodal/inputs.py

@@ -215,6 +215,9 @@ class MultiModalInputsV2(TypedDict):
     mm_kwargs: MultiModalKwargs
     """Keyword arguments to be directly passed to the model after batching."""
 
+    mm_hashes: NotRequired[List[str]]
+    """The hashes of the multi-modal data."""
+
     mm_placeholders: MultiModalPlaceholderDict
     """
     For each modality, information about the placeholder tokens in

vllm/v1/core/kv_cache_manager.py

@@ -4,7 +4,9 @@ from typing import Dict, Iterable, List, Optional
 from vllm.logger import init_logger
 from vllm.utils import cdiv
 from vllm.v1.core.kv_cache_utils import (BlockHashType, FreeKVCacheBlockQueue,
-                                         KVCacheBlock, hash_block_tokens,
+                                         KVCacheBlock,
+                                         generate_block_hash_extra_keys,
+                                         hash_block_tokens,
                                          hash_request_tokens)
 from vllm.v1.request import Request
 
@@ -83,10 +85,12 @@ class KVCacheManager:
 
         computed_blocks = []
 
-        # TODO(rickyx): potentially we could cache this so we don't have to
-        # recompute it every time.
-        block_hashes = hash_request_tokens(self.block_size,
-                                           request.all_token_ids)
+        # The block hashes for the request may already be computed
+        # if the request was preempted and resumed.
+        if not request.kv_block_hashes:
+            request.set_kv_block_hashes(
+                hash_request_tokens(self.block_size, request))
+        block_hashes = request.kv_block_hashes
 
         for block_hash in block_hashes:
             # block_hashes is a chain of block hashes. If a block hash is not
@@ -242,14 +246,16 @@ class KVCacheManager:
         num_computed_tokens = len(computed_blocks) * self.block_size
         num_full_blocks = (num_computed_tokens + num_tokens) // self.block_size
 
-        self._cache_full_blocks(
-            request=request,
-            blk_start_idx=len(computed_blocks),
-            # The new full blocks are the full blocks that are not computed.
-            full_blocks=self.req_to_blocks[request.request_id]
-            [len(computed_blocks):num_full_blocks],
-            prev_block=computed_blocks[-1] if computed_blocks else None,
-        )
+        new_full_blocks = self.req_to_blocks[
+            request.request_id][len(computed_blocks):num_full_blocks]
+        if new_full_blocks:
+            self._cache_full_blocks(
+                request=request,
+                blk_start_idx=len(computed_blocks),
+                # The new full blocks are the full blocks that are not computed.
+                full_blocks=new_full_blocks,
+                prev_block=computed_blocks[-1] if computed_blocks else None,
+            )
 
         return new_blocks
 
@@ -376,6 +382,8 @@ class KVCacheManager:
             full_blocks: The list of blocks to update hash metadata.
             prev_block: The previous block in the chain.
         """
+        num_cached_block_hashes = len(request.kv_block_hashes)
+
         # Update the new blocks with the block hashes through the chain.
         prev_block_hash_value = None
         if prev_block is not None:
@@ -387,17 +395,35 @@ class KVCacheManager:
         for i, blk in enumerate(full_blocks):
             blk_idx = blk_start_idx + i
 
-            block_tokens = request.all_token_ids[blk_idx *
-                                                 self.block_size:(blk_idx +
-                                                                  1) *
-                                                 self.block_size]
-            assert len(block_tokens) == self.block_size, (
-                f"Expected {self.block_size} tokens, got {len(block_tokens)} "
-                f"at {blk_idx}th block for request "
-                f"{request.request_id}({request})")
-
-            # Compute the hash of the current block.
-            block_hash = hash_block_tokens(prev_block_hash_value, block_tokens)
+            if blk_idx < num_cached_block_hashes:
+                # The block hash may already be computed in
+                # "get_computed_blocks" if the tokens are not generated by
+                # this request (either the prompt tokens or the previously
+                # generated tokens with preemption). In this case we simply
+                # reuse the block hash.
+                block_hash = request.kv_block_hashes[blk_idx]
+            else:
+                # Otherwise compute the block hash and cache it in the request
+                # in case it will be preempted in the future.
+                start_token_idx = blk_idx * self.block_size
+                end_token_idx = (blk_idx + 1) * self.block_size
+                block_tokens = request.all_token_ids[
+                    start_token_idx:end_token_idx]
+                assert len(block_tokens) == self.block_size, (
+                    f"Expected {self.block_size} tokens, got "
+                    f"{len(block_tokens)} at {blk_idx}th block for request "
+                    f"{request.request_id}({request})")
+
+                # Generate extra keys for multi-modal inputs. Note that since
+                # we reach to this branch only when the block is completed with
+                # generated tokens, we only need to consider the last mm input.
+                extra_keys, _ = generate_block_hash_extra_keys(
+                    request, start_token_idx, end_token_idx, -1)
+
+                # Compute the hash of the current block.
+                block_hash = hash_block_tokens(prev_block_hash_value,
+                                               block_tokens, extra_keys)
+                request.append_kv_block_hashes(block_hash)
 
             # Update and added the full block to the cache.
             blk.block_hash = block_hash

vllm/v1/core/kv_cache_utils.py

 """KV-Cache Utilities."""
 from collections.abc import Sequence
 from dataclasses import dataclass
-from typing import List, NamedTuple, Optional, Tuple
+from typing import Any, List, NamedTuple, Optional, Tuple
 
 from vllm.logger import init_logger
+from vllm.v1.request import Request
 
 logger = init_logger(__name__)
 
 
 class BlockHashType(NamedTuple):
-    """Hash value of a block and the token IDs in the block.
-    The reason we keep a tuple of token IDs is to make sure no hash
-    collision happens when the hash value is the same.
+    """Hash value of a block (int), the token IDs in the block, and extra keys.
+    The reason we keep a tuple of token IDs and extra keys is to make sure
+    no hash collision happens when the hash value is the same.
     """
+    # Hash value of the block in an integer.
     hash_value: int
+    # Token IDs in the block.
     token_ids: Tuple[int, ...]
+    # Extra keys for the block.
+    extra_keys: Optional[Any] = None
 
 
 @dataclass
@@ -159,8 +164,80 @@ class FreeKVCacheBlockQueue:
         return ret
 
 
-def hash_block_tokens(parent_block_hash: Optional[int],
-                      curr_block_token_ids: Sequence[int]) -> BlockHashType:
+def generate_block_hash_extra_keys(
+        request: Request, start_token_idx: int, end_token_idx: int,
+        start_mm_idx: int) -> Tuple[Optional[Tuple[Any, ...]], int]:
+    """Generate extra keys for the block hash. The extra keys can come from
+    the multi-modal inputs and request specific metadata (e.g., LoRA ID).
+    For multi-modal inputs, the extra keys are (mm_hash, start_offset) that
+    indicate a mm input contained in the block and its starting offset in
+    the block tokens.
+    
+    Args:
+        request: The request object.
+        start_token_idx: The start token index of the block.
+        end_token_idx: The end token index of the block.
+        start_mm_idx: The start multi-modal index of the block.
+    
+    Returns:
+        A tuple of extra keys and the next multi-modal index.
+    """
+
+    mm_positions, mm_hashes = request.mm_positions, request.mm_hashes
+    if not mm_positions:
+        return None, start_mm_idx
+
+    if mm_positions and len(mm_positions) != len(mm_hashes):
+        raise ValueError(
+            "The number of multi-modal positions and hashes must match. This "
+            "is likely because you do not enable MM preprocessor hashing. "
+            "Please set mm_cache_preprocessor=True.")
+
+    # Note that we assume mm_positions is sorted by offset.
+    # We do not need to check all mm inputs if the start token index is out of
+    # range. This usually happens in the late prefill phase and decoding phase.
+    if mm_positions[-1]["offset"] + mm_positions[-1][
+            "length"] < start_token_idx:
+        return None, start_mm_idx
+
+    # Support start_mm_idx == -1 to indicate the last mm input.
+    if start_mm_idx < 0:
+        assert -start_mm_idx <= len(mm_positions)
+        start_mm_idx = len(mm_positions) + start_mm_idx
+
+    extra_keys = []
+    curr_mm_idx = start_mm_idx
+    while mm_positions and curr_mm_idx < len(mm_positions):
+        assert mm_hashes[curr_mm_idx] is not None
+        offset = mm_positions[curr_mm_idx]["offset"]
+        length = mm_positions[curr_mm_idx]["length"]
+        if end_token_idx > offset:
+            if start_token_idx > offset + length:
+                # This block has passed the current mm input.
+                curr_mm_idx += 1
+                continue
+
+            # The block contains the current mm input.
+            mm_start = max(0, start_token_idx - offset)
+            extra_keys.append((mm_hashes[curr_mm_idx], mm_start))
+            if end_token_idx >= offset + length:
+                # If this block contains the end of the current mm input,
+                # move to the next mm input as this block may also contain
+                # the next mm input.
+                curr_mm_idx += 1
+            else:
+                # Otherwise this block is done with mm inputs.
+                break
+        else:
+            # This block has not reached the current mm input.
+            break
+    return tuple(extra_keys), curr_mm_idx
+
+
+def hash_block_tokens(
+        parent_block_hash: Optional[int],
+        curr_block_token_ids: Sequence[int],
+        extra_keys: Optional[Tuple[Any, ...]] = None) -> BlockHashType:
     """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. We use LRU cache for this function to avoid recomputing
@@ -174,27 +251,39 @@ def hash_block_tokens(parent_block_hash: Optional[int],
             if this is the first block.
         curr_block_token_ids: A list of token ids in the current
             block. The current block is assumed to be full.
+        extra_keys: Extra keys for the block.
 
     Returns:
         The hash value of the block and the token ids in the block.
         The entire tuple is used as the hash key of the block.
     """
     return BlockHashType(hash((parent_block_hash, *curr_block_token_ids)),
-                         tuple(curr_block_token_ids))
+                         tuple(curr_block_token_ids), extra_keys)
 
 
 def hash_request_tokens(block_size: int,
-                        token_ids: Sequence[int]) -> List[BlockHashType]:
+                        request: Request) -> List[BlockHashType]:
     """Computes hash values of a chain of blocks given a sequence of
     token IDs. The hash value is used for prefix caching.
 
     Args:
         block_size: The size of each block.
-        token_ids: A sequence of token ids in the request.
+        request: The request object.
 
     Returns:
         The list of computed hash values.
     """
+    token_ids = request.all_token_ids
+    mm_positions, mm_hashes = request.mm_positions, request.mm_hashes
+    if mm_positions and len(mm_positions) != len(mm_hashes):
+        raise ValueError(
+            "The number of multi-modal positions and hashes must match.")
+
+    # TODO: Extend this to support other features such as LoRA.
+    need_extra_keys = bool(mm_positions)
+    extra_keys = None
+    curr_mm_idx = 0
+
     ret = []
     parent_block_hash_value = None
     for start in range(0, len(token_ids), block_size):
@@ -203,8 +292,14 @@ def hash_request_tokens(block_size: int,
         # Do not hash the block if it is not full.
         if len(block_token_ids) < block_size:
             break
+
+        # Add extra keys if the block is a multi-modal block.
+        if need_extra_keys:
+            extra_keys, curr_mm_idx = generate_block_hash_extra_keys(
+                request, start, end, curr_mm_idx)
+
         block_hash = hash_block_tokens(parent_block_hash_value,
-                                       block_token_ids)
+                                       block_token_ids, extra_keys)
         ret.append(block_hash)
         parent_block_hash_value = block_hash.hash_value
     return ret

vllm/v1/core/scheduler.py

@@ -516,6 +516,7 @@ class NewRequestData:
     prompt_token_ids: List[int]
     prompt: Optional[str]
     mm_inputs: List["MultiModalKwargs"]
+    mm_hashes: List[str]
     mm_positions: List["PlaceholderRange"]
     sampling_params: SamplingParams
     block_ids: List[int]
@@ -533,6 +534,7 @@ class NewRequestData:
             prompt_token_ids=request.prompt_token_ids,
             prompt=request.prompt,
             mm_inputs=request.mm_inputs,
+            mm_hashes=request.mm_hashes,
             mm_positions=request.mm_positions,
             sampling_params=request.sampling_params,
             block_ids=block_ids,

vllm/v1/engine/async_llm.py

@@ -60,9 +60,13 @@ class AsyncLLM(EngineClient):
         self.client_aborted_requests: List[str] = []
 
         # Processor (converts Inputs --> EngineCoreRequests).
-        self.processor = Processor(vllm_config.model_config,
-                                   vllm_config.lora_config, self.tokenizer,
-                                   input_registry)
+        self.processor = Processor(
+            model_config=vllm_config.model_config,
+            cache_config=vllm_config.cache_config,
+            lora_config=vllm_config.lora_config,
+            tokenizer=self.tokenizer,
+            input_registry=input_registry,
+        )
 
         # Detokenizer (converts EngineCoreOutputs --> RequestOutput).
         self.detokenizer = Detokenizer(

vllm/v1/engine/core.py

@@ -65,7 +65,8 @@ class EngineCore:
 
         self._last_logging_time = time.time()
 
-        self.mm_input_mapper_server = MMInputMapperServer()
+        self.mm_input_mapper_server = MMInputMapperServer(
+            vllm_config.model_config)
 
     def _initialize_kv_caches(self,
                               cache_config: CacheConfig) -> Tuple[int, int]:
@@ -98,9 +99,8 @@ class EngineCore:
             # MM mapper, so anything that has a hash must have a HIT cache
             # entry here as well.
             assert request.mm_inputs is not None
-            request.mm_inputs, request.mm_hashes = (
-                self.mm_input_mapper_server.process_inputs(
-                    request.mm_inputs, request.mm_hashes))
+            request.mm_inputs = self.mm_input_mapper_server.process_inputs(
+                request.mm_inputs, request.mm_hashes)
 
         req = Request.from_engine_core_request(request)
 

vllm/v1/engine/llm_engine.py

@@ -55,9 +55,12 @@ class LLMEngine:
         self.tokenizer.ping()
 
         # Processor (convert Inputs --> EngineCoreRequests)
-        self.processor = Processor(vllm_config.model_config,
-                                   vllm_config.lora_config, self.tokenizer,
-                                   input_registry, mm_registry)
+        self.processor = Processor(model_config=vllm_config.model_config,
+                                   cache_config=vllm_config.cache_config,
+                                   lora_config=vllm_config.lora_config,
+                                   tokenizer=self.tokenizer,
+                                   input_registry=input_registry,
+                                   mm_registry=mm_registry)
 
         # Detokenizer (converts EngineCoreOutputs --> RequestOutput)
         self.detokenizer = Detokenizer(

vllm/v1/engine/mm_input_mapper.py

-from typing import Any, Dict, List, Optional, Tuple
+from typing import Any, Dict, List, Optional
 
 import PIL
 from blake3 import blake3
@@ -42,6 +42,8 @@ class MMInputMapperClient:
             model_config)
         self.mm_registry.init_mm_limits_per_prompt(model_config)
 
+        # Init cache
+        self.use_cache = model_config.mm_cache_preprocessor
         self.mm_cache = LRUDictCache[str, MultiModalKwargs](MM_CACHE_SIZE)
 
         # DEBUG: Set to None to disable
@@ -61,7 +63,7 @@ class MMInputMapperClient:
         mm_hashes: Optional[List[str]],
         mm_processor_kwargs: Optional[Dict[str, Any]],
         precomputed_mm_inputs: Optional[List[MultiModalKwargs]],
-    ) -> Tuple[List[MultiModalKwargs], Optional[List[str]]]:
+    ) -> List[MultiModalKwargs]:
         if precomputed_mm_inputs is None:
             image_inputs = mm_data["image"]
             if not isinstance(image_inputs, list):
@@ -70,26 +72,21 @@ class MMInputMapperClient:
         else:
             num_inputs = len(precomputed_mm_inputs)
 
-        # Check if hash is enabled
-        use_hash = mm_hashes is not None
-        if use_hash:
+        # Sanity
+        if self.use_cache:
             assert mm_hashes is not None
-            assert num_inputs == len(
-                mm_hashes), "num_inputs = {} len(mm_hashes) = {}".format(
-                    num_inputs, len(mm_hashes))
+            assert num_inputs == len(mm_hashes)
 
         # Process each image input separately, so that later we can schedule
         # them in a fine-grained manner.
         # Apply caching (if enabled) and reuse precomputed inputs (if provided)
-        ret_hashes: Optional[List[str]] = [] if use_hash else None
         ret_inputs: List[MultiModalKwargs] = []
         for input_id in range(num_inputs):
             if self.mm_debug_cache_hit_ratio_steps is not None:
                 self.cache_hit_ratio(self.mm_debug_cache_hit_ratio_steps)
 
-            mm_hash = None
             mm_input = None
-            if use_hash:
+            if self.use_cache:
                 assert mm_hashes is not None
                 mm_hash = mm_hashes[input_id]
                 mm_input = self.mm_cache.get(mm_hash)
@@ -106,7 +103,7 @@ class MMInputMapperClient:
                         mm_processor_kwargs=mm_processor_kwargs,
                     )
 
-                if use_hash:
+                if self.use_cache:
                     # Add to cache
                     assert mm_hash is not None
                     self.mm_cache.put(mm_hash, mm_input)
@@ -114,18 +111,15 @@ class MMInputMapperClient:
                 self.mm_cache_hits += 1
                 mm_input = None  # Avoids sending mm_input to Server
 
-            if use_hash:
-                assert mm_hash is not None
-                assert ret_hashes is not None
-                ret_hashes.append(mm_hash)
             ret_inputs.append(mm_input)
 
-        return ret_inputs, ret_hashes
+        return ret_inputs
 
 
 class MMInputMapperServer:
 
-    def __init__(self, ):
+    def __init__(self, model_config):
+        self.use_cache = model_config.mm_cache_preprocessor
         self.mm_cache = LRUDictCache[str, MultiModalKwargs](MM_CACHE_SIZE)
 
     def process_inputs(
@@ -135,6 +129,9 @@ class MMInputMapperServer:
     ) -> List[MultiModalKwargs]:
         assert len(mm_inputs) == len(mm_hashes)
 
+        if not self.use_cache:
+            return mm_inputs
+
         full_mm_inputs = []
         for mm_input, mm_hash in zip(mm_inputs, mm_hashes):
             assert mm_hash is not None

vllm/v1/engine/processor.py

 import time
 from typing import Any, Dict, Mapping, Optional, Tuple, Union
 
-from vllm.config import LoRAConfig, ModelConfig
+from vllm.config import CacheConfig, LoRAConfig, ModelConfig
 from vllm.inputs import (INPUT_REGISTRY, InputRegistry, ProcessorInputs,
                          PromptType, SingletonInputsAdapter)
 from vllm.inputs.parse import is_encoder_decoder_inputs
@@ -23,6 +23,7 @@ class Processor:
     def __init__(
         self,
         model_config: ModelConfig,
+        cache_config: CacheConfig,
         lora_config: Optional[LoRAConfig],
         tokenizer: BaseTokenizerGroup,
         input_registry: InputRegistry = INPUT_REGISTRY,
@@ -45,8 +46,9 @@ class Processor:
         self.mm_input_mapper_client = MMInputMapperClient(model_config)
 
         # Multi-modal hasher (for images)
-        self.mm_hasher = MMHasher(
-        ) if model_config.mm_cache_preprocessor else None
+        self.use_hash = model_config.mm_cache_preprocessor or \
+            cache_config.enable_prefix_caching
+        self.mm_hasher = MMHasher()
 
     # TODO: run in an ThreadpoolExecutor or BackgroundProcess.
     # This ideally should releases the GIL, so we should not block the
@@ -77,7 +79,7 @@ class Processor:
 
         # Compute MM hashes (if enabled)
         mm_hashes = None
-        if self.mm_hasher is not None:
+        if self.use_hash:
             mm_hashes = self.mm_hasher.hash(prompt)
 
         # Process inputs.
@@ -118,7 +120,7 @@ class Processor:
         # Apply MM mapper
         mm_inputs = None
         if len(decoder_inputs.multi_modal_data) > 0:
-            mm_inputs, mm_hashes = self.mm_input_mapper_client.process_inputs(
+            mm_inputs = self.mm_input_mapper_client.process_inputs(
                 decoder_inputs.multi_modal_data, mm_hashes,
                 decoder_inputs.mm_processor_kwargs, precomputed_mm_inputs)
 

vllm/v1/request.py

 import enum
-from typing import List, Optional, Union
+from typing import TYPE_CHECKING, List, Optional, Union
 
 from vllm.inputs import DecoderOnlyInputs, SingletonInputsAdapter, token_inputs
 from vllm.lora.request import LoRARequest
@@ -9,6 +9,9 @@ from vllm.sequence import RequestMetrics
 from vllm.v1.engine import EngineCoreRequest
 from vllm.v1.utils import ConstantList
 
+if TYPE_CHECKING:
+    from vllm.v1.core.kv_cache_utils import BlockHashType
+
 
 class Request:
 
@@ -45,6 +48,7 @@ class Request:
         self._all_token_ids: List[int] = self.prompt_token_ids.copy()
         self.num_computed_tokens = 0
 
+        # Multi-modal input metadata.
         mm_positions = self.inputs.multi_modal_placeholders
         if mm_positions:
             # FIXME(woosuk): Support other modalities.
@@ -56,6 +60,12 @@ class Request:
         if self.inputs.multi_modal_inputs:
             self.mm_inputs = self.inputs.multi_modal_inputs
 
+        self.mm_hashes: List[str] = self.inputs.multi_modal_hashes
+
+        # Cache the computed kv block hashes of the request to avoid
+        # recomputing.
+        self._kv_block_hashes: List[BlockHashType] = []
+
     @classmethod
     def from_engine_core_request(cls, request: EngineCoreRequest) -> "Request":
         return cls(
@@ -65,6 +75,7 @@ class Request:
                 prompt=request.prompt,
                 multi_modal_data=None,
                 multi_modal_inputs=request.mm_inputs,
+                multi_modal_hashes=request.mm_hashes,
                 multi_modal_placeholders=request.mm_placeholders,
                 mm_processor_kwargs=None,
             ),
@@ -121,6 +132,17 @@ class Request:
         num_tokens = self.mm_positions[input_id]["length"]
         return num_tokens
 
+    @property
+    def kv_block_hashes(self) -> ConstantList["BlockHashType"]:
+        # Prevent directly appending to the kv_block_hashes.
+        return ConstantList(self._kv_block_hashes)
+
+    def set_kv_block_hashes(self, value: List["BlockHashType"]) -> None:
+        self._kv_block_hashes = value
+
+    def append_kv_block_hashes(self, block_hash: "BlockHashType") -> None:
+        self._kv_block_hashes.append(block_hash)
+
 
 class RequestStatus(enum.IntEnum):
     """Status of a request."""