update v1 fa layout

vllm/attention/layer.py

@@ -75,7 +75,7 @@ class Attention(nn.Module):
             calculate_kv_scales = cache_config.calculate_kv_scales
         else:
             kv_cache_dtype = "auto"
-            block_size = 16 if not envs.VLLM_USE_FLASH_ATTN_PA else 64
+            block_size = 64 if envs.VLLM_USE_FLASH_ATTN_PA or envs.VLLM_USE_FLASH_MLA else 16
             is_attention_free = False
             calculate_kv_scales = False
         if num_kv_heads is None:
@@ -303,7 +303,7 @@ class MultiHeadAttention(nn.Module):
         attn_backend = get_attn_backend(head_size,
                                         dtype,
                                         kv_cache_dtype=None,
-                                        block_size=16 if not envs.VLLM_USE_FLASH_ATTN_PA else 64,
+                                        block_size=64 if envs.VLLM_USE_FLASH_ATTN_PA or envs.VLLM_USE_FLASH_MLA else 16,
                                         is_attention_free=False)
         backend = backend_name_to_enum(attn_backend.get_name())
         if current_platform.is_rocm():

vllm/attention/utils/fa_utils.py

@@ -15,8 +15,8 @@ if current_platform.is_cuda():
                                       get_scheduler_metadata)
 elif current_platform.is_rocm():
     from vllm import _custom_ops as ops
-    reshape_and_cache_flash = ops.reshape_and_cache_flash
-    from flash_attn import flash_attn_varlen_func, vllm_flash_attn_varlen_func
+    reshape_and_cache_cuda = ops.reshape_and_cache_cuda
+    from flash_attn import vllm_flash_attn_varlen_func
 elif current_platform.is_xpu():
     from vllm._ipex_ops import ipex_ops as ops
     reshape_and_cache_flash = ops.reshape_and_cache_flash

vllm/config.py

@@ -1497,7 +1497,7 @@ PrefixCachingHashAlgo = Literal["builtin", "sha256"]
 class CacheConfig:
     """Configuration for the KV cache."""
 
-    block_size: BlockSize = 16 if not envs.VLLM_USE_FLASH_ATTN_PA else 64  # type: ignore
+    block_size: BlockSize = 64 if envs.VLLM_USE_FLASH_ATTN_PA or envs.VLLM_USE_FLASH_MLA else 16  # type: ignore
     """Size of a contiguous cache block in number of tokens. This is ignored on
     neuron devices and set to `--max-model-len`. On CUDA devices, only block
     sizes up to 32 are supported. On HPU devices, block size defaults to 128.

vllm/v1/attention/backends/flash_attn.py

@@ -2,7 +2,7 @@
 # SPDX-FileCopyrightText: Copyright contributors to the vLLM project
 """Attention layer with FlashAttention."""
 from dataclasses import dataclass
-from typing import TYPE_CHECKING, Any, ClassVar, Optional
+from typing import TYPE_CHECKING, Any, ClassVar, Optional, Tuple
 
 import numpy as np
 import torch
@@ -25,9 +25,8 @@ if is_flash_attn_varlen_func_available():
                                                 get_scheduler_metadata,
                                                 reshape_and_cache_flash)
     else:
-        from vllm.attention.utils.fa_utils import (flash_attn_varlen_func,
-                                               vllm_flash_attn_varlen_func,
-                                               reshape_and_cache_flash)
+        from vllm.attention.utils.fa_utils import (vllm_flash_attn_varlen_func,
+                                               reshape_and_cache_cuda)
 
 from vllm.config import VllmConfig, get_layers_from_vllm_config
 
@@ -83,6 +82,7 @@ class FlashAttentionBackend(AttentionBackend):
     def get_builder_cls() -> type["FlashAttentionMetadataBuilder"]:
         return FlashAttentionMetadataBuilder
 
+    if not current_platform.is_rocm():
         @staticmethod
         def get_kv_cache_shape(
             num_blocks: int,
@@ -106,6 +106,35 @@ class FlashAttentionBackend(AttentionBackend):
             else:
                 raise ValueError(f"Unknown cache layout format {cache_layout}.")
             return stride_order
+    else:
+        @staticmethod
+        def get_kv_cache_shape(
+            num_blocks: int,
+            block_size: int,
+            num_kv_heads: int,
+            head_size: int,
+        ) -> tuple[tuple[int, ...], tuple[int, ...]]:
+            if block_size % 16 != 0:
+                raise ValueError("Block size must be a multiple of 16.")
+            return (
+                (num_blocks, num_kv_heads, block_size, head_size),
+                (num_blocks, num_kv_heads, head_size, block_size),
+            )
+
+        @staticmethod
+        def get_kv_cache_stride_order() -> tuple[tuple[int, ...], tuple[int, ...]]:
+            # `stride_order` indicates the permutation that gets
+            # us from `get_kv_cache_shape` to the actual memory layout we want.
+            cache_layout = get_kv_cache_layout()
+            if cache_layout == "NHD":
+                key_stride_order = (0, 1, 2, 3)
+                value_stride_order = (0, 1, 3, 2)
+            elif cache_layout == "HND":
+                key_stride_order = (0, 2, 1, 3)
+                value_stride_order = (0, 3, 1, 2)
+            else:
+                raise ValueError(f"Unknown cache layout format {cache_layout}.")
+            return key_stride_order, value_stride_order  
         
 
 @dataclass
@@ -512,7 +541,10 @@ class FlashAttentionImpl(AttentionImpl):
         # performance to make sure it does not introduce any overhead.
 
         num_actual_tokens = attn_metadata.num_actual_tokens
+        if not current_platform.is_rocm():
             key_cache, value_cache = kv_cache.unbind(0)
+        else:
+            key_cache, value_cache = kv_cache
 
         if self.kv_sharing_target_layer_name is None:
             # Reshape the input keys and values and store them in the cache.
@@ -522,6 +554,7 @@ class FlashAttentionImpl(AttentionImpl):
             # and value[:num_actual_tokens] because the reshape_and_cache_flash
             # op uses the slot_mapping's shape to determine the number of
             # actual tokens.
+            if not current_platform.is_rocm():
                 reshape_and_cache_flash(
                     key,
                     value,
@@ -532,6 +565,17 @@ class FlashAttentionImpl(AttentionImpl):
                     layer._k_scale,
                     layer._v_scale,
                 )
+            else:
+                reshape_and_cache_cuda(
+                    key,
+                    value,
+                    key_cache,
+                    value_cache,
+                    attn_metadata.slot_mapping,
+                    self.kv_cache_dtype,
+                    layer._k_scale,
+                    layer._v_scale,
+                )
 
         if self.kv_cache_dtype.startswith("fp8"):
             key_cache = key_cache.view(torch.float8_e4m3fn)
@@ -618,7 +662,7 @@ class FlashAttentionImpl(AttentionImpl):
                     # k_descale=layer._k_scale.expand(descale_shape),
                     # v_descale=layer._v_scale.expand(descale_shape),
                     # num_splits=attn_metadata.max_num_splits,
-                    is_prefix_cache=False,
+                    is_prefix_cache=True,
                 )
             return output
 

vllm/v1/worker/gpu_model_runner.py

@@ -2494,6 +2494,59 @@ class GPUModelRunner(LoRAModelRunnerMixin):
                               kv_cache_spec.page_size_bytes)
                 if isinstance(kv_cache_spec, AttentionSpec):
                     has_attn = True
+                    if envs.VLLM_USE_FLASH_ATTN_PA and not kv_cache_spec.use_mla:
+                        key_cache_shape, value_cache_shape = self.attn_backends[i].get_kv_cache_shape(
+                            num_blocks, kv_cache_spec.block_size,
+                            kv_cache_spec.num_kv_heads, kv_cache_spec.head_size)
+                        dtype = kv_cache_spec.dtype
+                        try:
+                            key_stride_order, value_stride_order = self.attn_backends[
+                                i].get_kv_cache_stride_order()
+                            assert len(key_stride_order) == len(
+                                key_cache_shape)
+                            assert len(value_stride_order) == len(
+                                value_cache_shape)
+                        except (AttributeError, NotImplementedError):
+                            key_stride_order = tuple(
+                                range(len(key_cache_shape)))
+                            value_stride_order = tuple(
+                                range(len(value_cache_shape)))
+                        # The allocation respects the backend-defined stride order
+                        # to ensure the semantic remains consistent for each
+                        # backend. We first obtain the generic kv cache shape and
+                        # then permute it according to the stride order which could
+                        # result in a non-contiguous tensor.
+                                                
+                        key_cache_shape = tuple(key_cache_shape[i]
+                                            for i in key_stride_order)
+                        value_cache_shape = tuple(value_cache_shape[i]
+                                            for i in value_stride_order)
+                        # Maintain original KV shape view.
+                        inv_key_order = [
+                            key_stride_order.index(i)
+                            for i in range(len(key_stride_order))
+                        ]
+                        inv_value_order = [
+                            value_stride_order.index(i)
+                            for i in range(len(value_stride_order))
+                        ]
+                        
+                        raw_tensor = kv_cache_raw_tensors[layer_name].view(dtype)
+                        total_elements = raw_tensor.numel()
+                        key_elements = (key_cache_shape[0] * key_cache_shape[1] * 
+                                        key_cache_shape[2] * key_cache_shape[3])
+                        value_elements = (value_cache_shape[0] * value_cache_shape[1] *
+                                        value_cache_shape[2] * value_cache_shape[3])
+
+                        assert total_elements == key_elements + value_elements
+
+                        key_cache = raw_tensor[:key_elements].view(key_cache_shape).permute(
+                            *inv_key_order)
+                        value_cache = raw_tensor[key_elements:].view(value_cache_shape).permute(
+                            *inv_value_order)
+                        
+                        kv_caches[layer_name] = (key_cache, value_cache)
+                    else:
                         kv_cache_shape = self.attn_backends[i].get_kv_cache_shape(
                             num_blocks, kv_cache_spec.block_size,
                             kv_cache_spec.num_kv_heads, kv_cache_spec.head_size)