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Add fast decode plan for flashinfer mla (#3987)

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This commit is contained in:
Baizhou Zhang
2025-03-02 19:16:37 -08:00
committed by GitHub
parent 7fbab730bd
commit fa56106731
9 changed files with 156 additions and 52 deletions
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python/sglang/srt/layers/attention/__init__.py
+2 -4
View File
@@ -29,9 +29,8 @@ class AttentionBackend(ABC):
num_tokens: int,
req_pool_indices: torch.Tensor,
seq_lens: torch.Tensor,
encoder_lens: Optional[torch.Tensor],
forward_mode: ForwardMode,
spec_info: Optional[SpecInfo],
**kwargs,
):
"""Init the metadata for a forward pass for capturing a cuda graph."""
raise NotImplementedError()
@@ -42,9 +41,8 @@ class AttentionBackend(ABC):
req_pool_indices: torch.Tensor,
seq_lens: torch.Tensor,
seq_lens_sum: int,
encoder_lens: Optional[torch.Tensor],
forward_mode: ForwardMode,
spec_info: Optional[SpecInfo],
**kwargs,
):
"""Init the metadata for a forward pass for replying a cuda graph."""
raise NotImplementedError()
python/sglang/srt/layers/attention/flashinfer_backend.py
+4 -2
View File
@@ -269,9 +269,10 @@ class FlashInferAttnBackend(AttentionBackend):
num_tokens: int,
req_pool_indices: torch.Tensor,
seq_lens: torch.Tensor,
encoder_lens: Optional[torch.Tensor],
forward_mode: ForwardMode,
encoder_lens: Optional[torch.Tensor],
spec_info: Optional[SpecInfo],
**kwargs,
):
if forward_mode.is_decode_or_idle():
decode_wrappers = []
@@ -339,9 +340,10 @@ class FlashInferAttnBackend(AttentionBackend):
req_pool_indices: torch.Tensor,
seq_lens: torch.Tensor,
seq_lens_sum: int,
encoder_lens: Optional[torch.Tensor],
forward_mode: ForwardMode,
encoder_lens: Optional[torch.Tensor],
spec_info: Optional[SpecInfo],
**kwargs,
):
if forward_mode.is_decode_or_idle():
self.indices_updater_decode.update(
python/sglang/srt/layers/attention/flashinfer_mla_backend.py
+118 -38
View File
@@ -10,6 +10,7 @@ More details can be found in https://docs.flashinfer.ai/api/mla.html
"""
from dataclasses import dataclass
from functools import partial
from typing import TYPE_CHECKING, Optional, Union
import torch
@@ -27,14 +28,12 @@ from sglang.srt.utils import is_flashinfer_available
if TYPE_CHECKING:
from sglang.srt.layers.radix_attention import RadixAttention
from sglang.srt.model_executor.model_runner import ModelRunner
from sglang.srt.speculative.spec_info import SpecInfo
if is_flashinfer_available():
from flashinfer import (
BatchMLAPagedAttentionWrapper,
BatchPrefillWithRaggedKVCacheWrapper,
)
from flashinfer.cascade import merge_state
@dataclass
@@ -63,6 +62,7 @@ class FlashInferMLAAttnBackend(AttentionBackend):
# Parse constants
self.max_context_len = model_runner.model_config.context_len
self.device = model_runner.device
global_config.enable_flashinfer_mla = True
@@ -85,10 +85,6 @@ class FlashInferMLAAttnBackend(AttentionBackend):
(max_bs + 1,), dtype=torch.int32, device=model_runner.device
)
self.kv_last_page_len = torch.ones(
(max_bs,), dtype=torch.int32, device=model_runner.device
)
self.q_indptr_decode = torch.arange(
0, max_bs + 1, dtype=torch.int32, device=model_runner.device
)
@@ -126,6 +122,7 @@ class FlashInferMLAAttnBackend(AttentionBackend):
forward_batch.seq_lens,
forward_batch.seq_lens_sum,
decode_wrapper=self.decode_wrapper,
init_metadata_replay=False,
)
self.forward_metadata = DecodeMetadata(self.decode_wrapper)
else:
@@ -161,13 +158,20 @@ class FlashInferMLAAttnBackend(AttentionBackend):
cuda_graph_kv_indices = kv_indices_buf
self.cuda_graph_kv_indices = cuda_graph_kv_indices
self.cuda_graph_custom_mask = torch.zeros(
(max_bs * self.max_context_len),
dtype=torch.uint8,
device="cuda",
self.cuda_graph_qo_indptr = self.q_indptr_decode.clone()
self.cuda_graph_kv_indptr = self.kv_indptr.clone()
self.cuda_graph_kv_lens = torch.ones(
(max_bs,), dtype=torch.int32, device=self.device
)
self.cuda_graph_qk_indptr = self.kv_indptr.clone()
self.cuda_graph_qo_indptr = self.kv_indptr.clone()
# For fast decode plan in graph replaying
self.cuda_graph_qo_indptr_cpu = self.cuda_graph_qo_indptr.to("cpu")
self.cuda_graph_kv_indptr_cpu = self.cuda_graph_kv_indptr.to("cpu")
self.fast_decode_kwargs = {
"qo_indptr_cpu": self.cuda_graph_qo_indptr_cpu,
"kv_indptr_cpu": self.cuda_graph_kv_indptr_cpu,
"kv_indices": self.cuda_graph_kv_indices,
}
def init_forward_metadata_capture_cuda_graph(
self,
@@ -175,18 +179,17 @@ class FlashInferMLAAttnBackend(AttentionBackend):
num_tokens: int,
req_pool_indices: torch.Tensor,
seq_lens: torch.Tensor,
encoder_lens: Optional[torch.Tensor],
forward_mode: ForwardMode,
spec_info: Optional[SpecInfo],
**kwargs,
):
if forward_mode.is_decode_or_idle():
decode_wrapper = BatchMLAPagedAttentionWrapper(
self.workspace_buffer,
use_cuda_graph=True,
qo_indptr=self.qo_indptr[: num_tokens + 1],
kv_indptr=self.kv_indptr[: num_tokens + 1],
qo_indptr=self.cuda_graph_qo_indptr[: num_tokens + 1],
kv_indptr=self.cuda_graph_kv_indptr[: num_tokens + 1],
kv_indices=self.cuda_graph_kv_indices,
kv_len_arr=self.kv_last_page_len[:num_tokens],
kv_len_arr=self.cuda_graph_kv_lens[:num_tokens],
backend="auto",
)
@@ -196,9 +199,11 @@ class FlashInferMLAAttnBackend(AttentionBackend):
seq_lens,
seq_lens_sum,
decode_wrapper=decode_wrapper,
init_metadata_replay=False,
)
self.decode_cuda_graph_metadata[bs] = decode_wrapper
self.forward_metadata = DecodeMetadata(decode_wrapper)
decode_wrapper.plan = partial(fast_mla_decode_plan, decode_wrapper)
else:
raise ValueError(f"Invalid mode: {forward_mode=}")
@@ -208,16 +213,30 @@ class FlashInferMLAAttnBackend(AttentionBackend):
req_pool_indices: torch.Tensor,
seq_lens: torch.Tensor,
seq_lens_sum: int,
encoder_lens: Optional[torch.Tensor],
forward_mode: ForwardMode,
spec_info: Optional[SpecInfo],
seq_lens_cpu: torch.Tensor,
**kwargs,
):
if forward_mode.is_decode_or_idle():
kv_len_arr_cpu = seq_lens_cpu[:bs]
self.cuda_graph_kv_indptr_cpu[1 : bs + 1] = torch.cumsum(
kv_len_arr_cpu, dim=0
)
self.fast_decode_kwargs.update(
{
"qo_indptr_cpu": self.cuda_graph_qo_indptr_cpu[: bs + 1],
"kv_indptr_cpu": self.cuda_graph_kv_indptr_cpu[: bs + 1],
"kv_len_arr_cpu": kv_len_arr_cpu,
}
)
self.indices_updater_decode.update(
req_pool_indices[:bs],
seq_lens[:bs],
seq_lens_sum,
decode_wrapper=self.decode_cuda_graph_metadata[bs],
init_metadata_replay=True,
**self.fast_decode_kwargs,
)
else:
raise ValueError(f"Invalid forward mode: {forward_mode=}")
@@ -317,7 +336,6 @@ class FlashInferMLAIndicesUpdaterDecode:
# Buffers and wrappers
self.kv_indptr = attn_backend.kv_indptr
self.kv_last_page_len = attn_backend.kv_last_page_len
self.req_to_token = model_runner.req_to_token_pool.req_to_token
self.q_indptr = attn_backend.q_indptr_decode
@@ -327,6 +345,8 @@ class FlashInferMLAIndicesUpdaterDecode:
seq_lens: torch.Tensor,
seq_lens_sum: int,
decode_wrapper: BatchMLAPagedAttentionWrapper,
init_metadata_replay: bool = False,
**fast_decode_kwargs,
):
decode_wrapper = decode_wrapper or self.decode_wrapper
self.call_begin_forward(
@@ -336,6 +356,8 @@ class FlashInferMLAIndicesUpdaterDecode:
seq_lens_sum,
self.q_indptr,
self.kv_indptr,
init_metadata_replay,
**fast_decode_kwargs,
)
def call_begin_forward(
@@ -346,14 +368,19 @@ class FlashInferMLAIndicesUpdaterDecode:
paged_kernel_lens_sum: int,
q_indptr: torch.Tensor,
kv_indptr: torch.Tensor,
init_metadata_replay: bool = False,
**fast_decode_kwargs,
):
bs = len(req_pool_indices)
q_indptr = q_indptr[: bs + 1]
kv_indptr[1 : bs + 1] = torch.cumsum(paged_kernel_lens, dim=0)
kv_indptr = kv_indptr[: bs + 1]
kv_indices = torch.empty(
paged_kernel_lens_sum, dtype=torch.int32, device="cuda"
kv_indices = (
torch.empty(paged_kernel_lens_sum, dtype=torch.int32, device="cuda")
if not init_metadata_replay
else fast_decode_kwargs["kv_indices"]
)
kv_lens = paged_kernel_lens.to(torch.int32)
sm_scale = self.scaling
@@ -366,21 +393,36 @@ class FlashInferMLAIndicesUpdaterDecode:
kv_indices,
self.req_to_token.shape[1],
)
wrapper.plan(
q_indptr,
kv_indptr,
kv_indices,
kv_lens,
self.num_local_heads,
self.kv_lora_rank,
self.qk_rope_head_dim,
1,
False,
sm_scale,
self.data_type,
self.data_type,
)
if not init_metadata_replay:
wrapper.plan(
q_indptr,
kv_indptr,
kv_indices,
kv_lens,
self.num_local_heads,
self.kv_lora_rank,
self.qk_rope_head_dim,
1,
False,
sm_scale,
self.data_type,
self.data_type,
)
else:
wrapper.plan(
fast_decode_kwargs["qo_indptr_cpu"],
fast_decode_kwargs["kv_indptr_cpu"],
kv_indices,
fast_decode_kwargs["kv_len_arr_cpu"],
self.num_local_heads,
self.kv_lora_rank,
self.qk_rope_head_dim,
1,
False,
sm_scale,
self.data_type,
self.data_type,
)
class FlashInferMLAIndicesUpdaterPrefill:
@@ -400,7 +442,6 @@ class FlashInferMLAIndicesUpdaterPrefill:
# Buffers and wrappers
self.kv_indptr = attn_backend.kv_indptr
self.kv_last_page_len = attn_backend.kv_last_page_len
self.qo_indptr = attn_backend.qo_indptr
self.req_to_token = model_runner.req_to_token_pool.req_to_token
self.prefill_wrapper_ragged = attn_backend.prefill_wrapper_ragged
@@ -497,3 +538,42 @@ class FlashInferMLAIndicesUpdaterPrefill:
self.q_data_type,
self.data_type,
)
def fast_mla_decode_plan(
self,
qo_indptr_cpu: torch.Tensor,
kv_indptr_cpu: torch.Tensor,
kv_indices: torch.Tensor,
kv_len_arr_cpu: torch.Tensor,
num_heads: int,
head_dim_ckv: int,
head_dim_kpe: int,
page_size: int,
causal: bool,
sm_scale: float,
q_data_type: torch.dtype,
kv_data_type: torch.dtype,
) -> None:
"""A faster version of BatchMLAPagedAttentionWrapper::plan,
for skipping the stream synchronization in original plan function during
cuda graph replaying.
"""
self._causal = causal
self._page_size = page_size
self._sm_scale = sm_scale
with self.device as device:
stream = torch.cuda.current_stream(device).cuda_stream
self._cached_module.plan(
self._float_workspace_buffer,
self._int_workspace_buffer,
self._pin_memory_int_workspace_buffer,
qo_indptr_cpu,
kv_indptr_cpu,
kv_len_arr_cpu,
num_heads,
head_dim_ckv,
causal,
stream,
)
python/sglang/srt/layers/attention/triton_backend.py
+4 -2
View File
@@ -230,9 +230,10 @@ class TritonAttnBackend(AttentionBackend):
num_tokens: int,
req_pool_indices: torch.Tensor,
seq_lens: torch.Tensor,
encoder_lens: Optional[torch.Tensor],
forward_mode: ForwardMode,
encoder_lens: Optional[torch.Tensor],
spec_info: Optional[SpecInfo],
**kwargs,
):
assert encoder_lens is None, "Not supported"
@@ -308,9 +309,10 @@ class TritonAttnBackend(AttentionBackend):
req_pool_indices: torch.Tensor,
seq_lens: torch.Tensor,
seq_lens_sum: int,
encoder_lens: Optional[torch.Tensor],
forward_mode: ForwardMode,
encoder_lens: Optional[torch.Tensor],
spec_info: Optional[SpecInfo],
**kwargs,
):
# NOTE: encoder_lens expected to be zeros or None
if forward_mode.is_decode_or_idle():