Sync from v0.13

vllm/attention/ops/vit_attn_wrappers.py

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+# SPDX-License-Identifier: Apache-2.0
+# SPDX-FileCopyrightText: Copyright contributors to the vLLM project
+"""
+This file contains ops for ViT attention to be compatible with torch.compile
+as there are operations here not supported by torch.compile (for instance,
+`.item()` in flash attention)
+
+Using these ops and wrapping vision blocks with `torch.compile` can speed up
+throughput in vision models by ~5% relative on H100, and improve token
+latencies by ~7% (see qwen2_5_vl for example usage)
+
+To use these ops, you must have a recent version of PyTorch installed (>= 2.4.0)
+"""
+
+import einops
+import torch
+import torch.nn.functional as F
+
+from vllm.platforms import current_platform
+from vllm.utils.torch_utils import direct_register_custom_op
+
+
+def flash_attn_maxseqlen_wrapper(
+    q: torch.Tensor,
+    k: torch.Tensor,
+    v: torch.Tensor,
+    cu_seqlens: torch.Tensor,
+    max_seqlen: torch.Tensor,
+    batch_size: int,
+    is_rocm_aiter: bool,
+) -> torch.Tensor:
+    if is_rocm_aiter:
+        from aiter import flash_attn_varlen_func
+    else:
+        from vllm.attention.utils.fa_utils import flash_attn_varlen_func
+    q, k, v = (einops.rearrange(x, "b s ... -> (b s) ...") for x in [q, k, v])
+    output = flash_attn_varlen_func(
+        q,
+        k,
+        v,
+        cu_seqlens_q=cu_seqlens,
+        cu_seqlens_k=cu_seqlens,
+        max_seqlen_q=max_seqlen.item(),
+        max_seqlen_k=max_seqlen.item(),
+        dropout_p=0.0,
+        causal=False,
+    )
+    context_layer = einops.rearrange(output, "(b s) h d -> b s h d", b=batch_size)
+    return context_layer
+
+
+def flash_attn_maxseqlen_wrapper_fake(
+    q: torch.Tensor,
+    k: torch.Tensor,
+    v: torch.Tensor,
+    cu_seqlens: torch.Tensor,
+    max_seqlen: torch.Tensor,
+    batch_size: int,
+    is_rocm_aiter: bool,
+) -> torch.Tensor:
+    return torch.empty_like(q)
+
+
+direct_register_custom_op(
+    op_name="flash_attn_maxseqlen_wrapper",
+    op_func=flash_attn_maxseqlen_wrapper,
+    fake_impl=flash_attn_maxseqlen_wrapper_fake,
+)
+
+
+def vit_flash_attn_wrapper(
+    q: torch.Tensor,
+    k: torch.Tensor,
+    v: torch.Tensor,
+    cu_seqlens: torch.Tensor,
+    max_seqlen: torch.Tensor,
+    batch_size: int,
+    is_rocm_aiter: bool,
+) -> torch.Tensor:
+    return torch.ops.vllm.flash_attn_maxseqlen_wrapper(
+        q, k, v, cu_seqlens, max_seqlen, batch_size, is_rocm_aiter
+    )
+
+
+# TODO: Once we have a torch 2.10, we can use tensor slices
+# so we won't need to wrap this in custom ops
+def torch_sdpa_wrapper(
+    q: torch.Tensor,
+    k: torch.Tensor,
+    v: torch.Tensor,
+    cu_seqlens: torch.Tensor,
+) -> torch.Tensor:
+    # Never remove the contiguous logic for ROCm
+    # Without it, hallucinations occur with the backend
+    if current_platform.is_rocm():
+        q = q.contiguous()
+        k = k.contiguous()
+        v = v.contiguous()
+
+    outputs = []
+
+    lens = (cu_seqlens[1:] - cu_seqlens[:-1]).tolist()
+    q_chunks = torch.split(q, lens, dim=1)
+    k_chunks = torch.split(k, lens, dim=1)
+    v_chunks = torch.split(v, lens, dim=1)
+    for q_i, k_i, v_i in zip(q_chunks, k_chunks, v_chunks):
+        q_i, k_i, v_i = (
+            einops.rearrange(x, "b s h d -> b h s d") for x in [q_i, k_i, v_i]
+        )
+        output_i = F.scaled_dot_product_attention(q_i, k_i, v_i, dropout_p=0.0)
+        output_i = einops.rearrange(output_i, "b h s d -> b s h d ")
+        outputs.append(output_i)
+    context_layer = torch.cat(outputs, dim=1)
+    return context_layer
+
+
+def torch_sdpa_wrapper_fake(
+    q: torch.Tensor,
+    k: torch.Tensor,
+    v: torch.Tensor,
+    cu_seqlens: torch.Tensor,
+) -> torch.Tensor:
+    return torch.empty_like(q)
+
+
+direct_register_custom_op(
+    op_name="torch_sdpa_wrapper",
+    op_func=torch_sdpa_wrapper,
+    fake_impl=torch_sdpa_wrapper_fake,
+)
+
+
+def vit_torch_sdpa_wrapper(
+    q: torch.Tensor,
+    k: torch.Tensor,
+    v: torch.Tensor,
+    cu_seqlens: torch.Tensor,
+) -> torch.Tensor:
+    return torch.ops.vllm.torch_sdpa_wrapper(q, k, v, cu_seqlens)