[Kernel] Support deep_gemm for linear methods (#19085)

Signed-off-by: artetaout <lulala341@gmail.com>

Author: artetaout

vllm/model_executor/layers/quantization/deepgemm.py

@@ -0,0 +1,84 @@
+# SPDX-License-Identifier: Apache-2.0
+import importlib.util
+import logging
+
+import torch
+
+from vllm.platforms import current_platform
+from vllm.triton_utils import triton
+from vllm.utils import direct_register_custom_op
+
+has_deep_gemm = importlib.util.find_spec("deep_gemm") is not None
+if has_deep_gemm:
+    import deep_gemm
+
+logger = logging.getLogger(__name__)
+
+
+def prepare_block_fp8_matmul_inputs(
+    A: torch.Tensor,
+    B: torch.Tensor,
+    As: torch.Tensor,
+    Bs: torch.Tensor,
+    block_size: list[int],
+    output_dtype: torch.dtype = torch.float16,
+) -> tuple[int, int, int, torch.Tensor]:
+    assert len(block_size) == 2
+    block_n, block_k = block_size[0], block_size[1]
+
+    assert A.shape[-1] == B.shape[-1]
+    assert A.shape[:-1] == As.shape[:-1]
+    assert A.is_contiguous()
+    assert triton.cdiv(A.shape[-1], block_k) == As.shape[-1]
+
+    M = A.numel() // A.shape[-1]
+
+    assert B.ndim == 2
+    assert B.is_contiguous()
+    assert Bs.ndim == 2
+    N, K = B.shape
+    assert triton.cdiv(N, block_n) == Bs.shape[0]
+    assert triton.cdiv(K, block_k) == Bs.shape[1]
+
+    C_shape = A.shape[:-1] + (N, )
+    C = A.new_empty(C_shape, dtype=output_dtype)
+
+    return M, N, K, C
+
+
+def w8a8_block_fp8_matmul_deepgemm(
+    A: torch.Tensor,
+    B: torch.Tensor,
+    As: torch.Tensor,
+    Bs: torch.Tensor,
+    block_size: list[int],
+    output_dtype: torch.dtype,
+) -> torch.Tensor:
+    M, N, K, C = prepare_block_fp8_matmul_inputs(A, B, As, Bs, block_size,
+                                                 output_dtype)
+    # Deepgemm only supports output tensor type as bfloat16
+    assert C.dtype == torch.bfloat16
+    deep_gemm.gemm_fp8_fp8_bf16_nt((A, As), (B, Bs), C)
+    return C
+
+
+def w8a8_block_fp8_matmul_deepgemm_fake(
+    A: torch.Tensor,
+    B: torch.Tensor,
+    As: torch.Tensor,
+    Bs: torch.Tensor,
+    block_size: list[int],
+    output_dtype: torch.dtype,
+) -> torch.Tensor:
+    M, N, K, C = prepare_block_fp8_matmul_inputs(A, B, As, Bs, block_size,
+                                                 output_dtype)
+    return C
+
+
+direct_register_custom_op(
+    op_name="w8a8_block_fp8_matmul_deepgemm",
+    op_func=w8a8_block_fp8_matmul_deepgemm,
+    mutates_args=[],
+    fake_impl=w8a8_block_fp8_matmul_deepgemm_fake,
+    dispatch_key=current_platform.dispatch_key,
+)

vllm/model_executor/layers/quantization/fp8.py

@@ -402,6 +402,7 @@ def apply(self,
 
         if self.block_quant:
             assert self.quant_config.weight_block_size is not None
+
             return torch.ops.vllm.apply_w8a8_block_fp8_linear(
                 input=x,
                 weight=layer.weight,

vllm/model_executor/layers/quantization/utils/fp8_utils.py

@@ -3,12 +3,14 @@
 
 # Adapted from https://github.com/sgl-project/sglang/pull/2575
 import functools
+import importlib.util
 import json
 import os
 from typing import Any, Callable, Optional, Union
 
 import torch
 
+import vllm.envs as envs
 from vllm import _custom_ops as ops
 from vllm.logger import init_logger
 from vllm.model_executor.layers.quantization.utils.quant_utils import (
@@ -20,6 +22,7 @@
 from vllm.utils import direct_register_custom_op
 
 logger = init_logger(__name__)
+has_deep_gemm = importlib.util.find_spec("deep_gemm") is not None
 
 
 def is_fp8(x: Union[torch.dtype, torch.Tensor]) -> bool:
@@ -98,6 +101,19 @@ def dispatch_w8a8_blockscale_func(
     return w8a8_block_fp8_matmul
 
 
+def should_use_deepgemm(output_dtype: torch.dtype, weight: torch.Tensor):
+    """
+    Check if DeepGEMM should be used based on the output dtype and weight shape.
+    DeepGEMM is only supported for bfloat16 output dtype and weights with shape
+    divisible by 128.
+    """
+
+    return (current_platform.is_cuda()
+            and current_platform.is_device_capability(90) and has_deep_gemm
+            and envs.VLLM_USE_DEEP_GEMM and output_dtype == torch.bfloat16
+            and weight.shape[0] % 128 == 0 and weight.shape[1] % 128 == 0)
+
+
 # TODO fix ROCm->Triton custom path:
 #  https://github.com/vllm-project/vllm/issues/14397
 def apply_w8a8_block_fp8_linear(
@@ -114,6 +130,29 @@ def apply_w8a8_block_fp8_linear(
     # View input as 2D matrix for fp8 methods
     input_2d = input.view(-1, input.shape[-1])
     output_shape = [*input.shape[:-1], weight.shape[0]]
+    output_dtype = input.dtype
+
+    if should_use_deepgemm(output_dtype, weight):
+
+        input_2d = input.view(-1, input.shape[-1])
+        output_shape = [*input.shape[:-1], weight.shape[0]]
+
+        q_input, x_scale = per_token_group_quant_fp8(
+            input_2d,
+            block_size[1],
+            column_major_scales=True,
+        )
+
+        output = torch.ops.vllm.w8a8_block_fp8_matmul_deepgemm(
+            q_input,
+            weight,
+            x_scale,
+            weight_scale,
+            block_size,
+            output_dtype=output_dtype)
+        if bias is not None:
+            output += bias
+        return output.to(dtype=output_dtype).view(*output_shape)
 
     if current_platform.is_cuda():
         if current_platform.has_device_capability(100):
@@ -134,7 +173,6 @@ def ceil_div(x: int, y: int) -> int:
 
     w8a8_blockscale_func = dispatch_w8a8_blockscale_func(
         use_cutlass, use_aiter_and_is_supported)
-
     if use_cutlass:
         q_input, x_scale = per_token_group_quant_fp8(
             input_2d, block_size[1], column_major_scales=use_cutlass)