chatai/sglang/python/sglang/srt/layers/attention/flashinfer_backend.py

1260 lines
45 KiB
Python

from __future__ import annotations
"""
Support different attention backends.
Now there are two backends: FlashInfer and Triton.
FlashInfer is faster and Triton is easier to customize.
Each backend supports two operators: extend (i.e. prefill with cached prefix) and decode.
"""
import os
from dataclasses import dataclass
from enum import Enum, auto
from functools import partial
from typing import TYPE_CHECKING, Callable, List, Optional, Union
import torch
import triton
from sglang.global_config import global_config
from sglang.srt.layers.attention.base_attn_backend import AttentionBackend
from sglang.srt.layers.attention.utils import create_flashinfer_kv_indices_triton
from sglang.srt.layers.dp_attention import get_attention_tp_size
from sglang.srt.model_executor.forward_batch_info import ForwardBatch, ForwardMode
from sglang.srt.speculative.eagle_utils import EagleDraftInput, EagleVerifyInput
from sglang.srt.utils import get_bool_env_var, is_flashinfer_available
if TYPE_CHECKING:
from sglang.srt.layers.radix_attention import RadixAttention
from sglang.srt.model_executor.model_runner import ModelRunner
if is_flashinfer_available():
from flashinfer import (
BatchDecodeWithPagedKVCacheWrapper,
BatchPrefillWithPagedKVCacheWrapper,
BatchPrefillWithRaggedKVCacheWrapper,
)
from flashinfer.cascade import merge_state
from flashinfer.decode import _get_range_buf, get_seq_lens
class WrapperDispatch(Enum):
SLIDING_WINDOW = auto()
CROSS_ATTENTION = auto()
@dataclass
class DecodeMetadata:
decode_wrappers: List[BatchDecodeWithPagedKVCacheWrapper]
@dataclass
class PrefillMetadata:
prefill_wrappers: List[BatchPrefillWithPagedKVCacheWrapper]
use_ragged: bool
extend_no_prefix: bool
# Reuse this workspace buffer across all flashinfer wrappers
global_workspace_buffer = None
class FlashInferAttnBackend(AttentionBackend):
"""Flashinfer attention kernels."""
def __init__(
self,
model_runner: ModelRunner,
skip_prefill: bool = False,
kv_indptr_buf: Optional[torch.Tensor] = None,
kv_last_page_len_buf: Optional[torch.Tensor] = None,
):
super().__init__()
# Parse constants
self.decode_use_tensor_cores = should_use_tensor_core(
kv_cache_dtype=model_runner.kv_cache_dtype,
num_attention_heads=model_runner.model_config.num_attention_heads
// get_attention_tp_size(),
num_kv_heads=model_runner.model_config.get_num_kv_heads(
get_attention_tp_size()
),
)
self.max_context_len = model_runner.model_config.context_len
self.skip_prefill = skip_prefill
self.is_multimodal = model_runner.model_config.is_multimodal
assert not (
model_runner.sliding_window_size is not None
and model_runner.model_config.is_encoder_decoder
), "Sliding window and cross attention are not supported together"
if model_runner.sliding_window_size is not None:
self.num_wrappers = 2
self.dispatch_reason = WrapperDispatch.SLIDING_WINDOW
elif model_runner.model_config.is_encoder_decoder:
self.num_wrappers = 2
self.dispatch_reason = WrapperDispatch.CROSS_ATTENTION
else:
self.num_wrappers = 1
self.dispatch_reason = None
# Qwen2 models require higher flashinfer workspace size
if "Qwen2ForCausalLM" in model_runner.model_config.hf_config.architectures:
global_config.flashinfer_workspace_size = 512 * 1024 * 1024
# Allocate buffers
global global_workspace_buffer
if global_workspace_buffer is None:
global_workspace_buffer = torch.empty(
global_config.flashinfer_workspace_size,
dtype=torch.uint8,
device=model_runner.device,
)
self.workspace_buffer = global_workspace_buffer
max_bs = model_runner.req_to_token_pool.size
if kv_indptr_buf is None:
self.kv_indptr = [
torch.zeros(
(max_bs + 1,), dtype=torch.int32, device=model_runner.device
)
for _ in range(self.num_wrappers)
]
else:
assert self.num_wrappers == 1
self.kv_indptr = [kv_indptr_buf]
if kv_last_page_len_buf is None:
self.kv_last_page_len = torch.ones(
(max_bs,), dtype=torch.int32, device=model_runner.device
)
else:
assert self.num_wrappers == 1
self.kv_last_page_len = kv_last_page_len_buf
if not self.skip_prefill:
self.qo_indptr = [
torch.zeros(
(max_bs + 1,), dtype=torch.int32, device=model_runner.device
)
for _ in range(self.num_wrappers)
]
self.prefill_wrapper_ragged = BatchPrefillWithRaggedKVCacheWrapper(
self.workspace_buffer, "NHD"
)
# Two wrappers: one for sliding window attention and one for full attention.
# Using two wrappers is unnecessary in the current PR, but are prepared for future PRs
self.prefill_wrappers_paged = []
self.prefill_wrappers_verify = []
self.decode_wrappers = []
for _ in range(self.num_wrappers):
if not skip_prefill:
self.prefill_wrappers_paged.append(
BatchPrefillWithPagedKVCacheWrapper(
self.workspace_buffer,
"NHD",
backend="fa2",
)
)
self.prefill_wrappers_verify.append(
BatchPrefillWithPagedKVCacheWrapper(
self.workspace_buffer,
"NHD",
)
)
self.decode_wrappers.append(
BatchDecodeWithPagedKVCacheWrapper(
self.workspace_buffer,
"NHD",
use_tensor_cores=self.decode_use_tensor_cores,
)
)
# Create indices updater
if not skip_prefill:
self.indices_updater_prefill = FlashInferIndicesUpdaterPrefill(
model_runner, self
) # for verify
self.indices_updater_decode = FlashInferIndicesUpdaterDecode(model_runner, self)
# Other metadata
self.forward_metadata: Union[PrefillMetadata, DecodeMetadata] = None
self.decode_cuda_graph_metadata = {}
self.prefill_cuda_graph_metadata = {} # For verify
self.draft_extend_cuda_graph_metadata = {} # For draft extend
def init_forward_metadata(self, forward_batch: ForwardBatch):
if forward_batch.forward_mode.is_decode_or_idle():
self.indices_updater_decode.update(
forward_batch.req_pool_indices,
forward_batch.seq_lens,
forward_batch.seq_lens_sum,
decode_wrappers=self.decode_wrappers,
encoder_lens=forward_batch.encoder_lens,
spec_info=forward_batch.spec_info,
)
self.forward_metadata = DecodeMetadata(self.decode_wrappers)
elif forward_batch.forward_mode.is_draft_extend():
self.indices_updater_prefill.update(
forward_batch.req_pool_indices,
forward_batch.seq_lens,
forward_batch.seq_lens_sum,
prefix_lens=None,
prefill_wrappers=self.prefill_wrappers_paged,
use_ragged=False,
encoder_lens=forward_batch.encoder_lens,
spec_info=forward_batch.spec_info,
)
self.forward_metadata = PrefillMetadata(
self.prefill_wrappers_paged, False, False
)
elif forward_batch.forward_mode.is_target_verify():
self.indices_updater_prefill.update(
forward_batch.req_pool_indices,
forward_batch.seq_lens,
forward_batch.seq_lens_sum,
prefix_lens=None,
prefill_wrappers=self.prefill_wrappers_verify,
use_ragged=False,
encoder_lens=forward_batch.encoder_lens,
spec_info=forward_batch.spec_info,
)
self.forward_metadata = PrefillMetadata(
self.prefill_wrappers_verify, False, False
)
else:
prefix_lens = forward_batch.extend_prefix_lens
if self.is_multimodal:
use_ragged = False
extend_no_prefix = False
else:
use_ragged = True
extend_no_prefix = not any(forward_batch.extend_prefix_lens_cpu)
self.indices_updater_prefill.update(
forward_batch.req_pool_indices,
forward_batch.seq_lens,
forward_batch.seq_lens_sum,
prefix_lens,
prefill_wrappers=self.prefill_wrappers_paged,
use_ragged=use_ragged,
encoder_lens=forward_batch.encoder_lens,
spec_info=None,
)
self.forward_metadata = PrefillMetadata(
self.prefill_wrappers_paged, use_ragged, extend_no_prefix
)
def init_cuda_graph_state(
self, max_bs: int, kv_indices_buf: Optional[torch.Tensor] = None
):
if kv_indices_buf is None:
cuda_graph_kv_indices = torch.zeros(
(max_bs * self.max_context_len,),
dtype=torch.int32,
device="cuda",
)
else:
cuda_graph_kv_indices = kv_indices_buf
self.cuda_graph_kv_indices = [cuda_graph_kv_indices] + [
cuda_graph_kv_indices.clone() for _ in range(self.num_wrappers - 1)
]
if not self.skip_prefill:
self.cuda_graph_custom_mask = torch.zeros(
(max_bs * self.max_context_len),
dtype=torch.uint8,
device="cuda",
)
self.cuda_graph_qk_indptr = [x.clone() for x in self.kv_indptr]
self.cuda_graph_qo_indptr = [x.clone() for x in self.kv_indptr]
def init_forward_metadata_capture_cuda_graph(
self,
bs: int,
num_tokens: int,
req_pool_indices: torch.Tensor,
seq_lens: torch.Tensor,
encoder_lens: Optional[torch.Tensor],
forward_mode: ForwardMode,
spec_info: Optional[Union[EagleDraftInput, EagleVerifyInput]],
):
if forward_mode.is_decode_or_idle():
decode_wrappers = []
for i in range(self.num_wrappers):
decode_wrappers.append(
BatchDecodeWithPagedKVCacheWrapper(
self.workspace_buffer,
"NHD",
use_cuda_graph=True,
use_tensor_cores=self.decode_use_tensor_cores,
paged_kv_indptr_buffer=self.kv_indptr[i][: num_tokens + 1],
paged_kv_indices_buffer=self.cuda_graph_kv_indices[i],
paged_kv_last_page_len_buffer=self.kv_last_page_len[
:num_tokens
],
)
)
seq_lens_sum = seq_lens.sum().item()
self.indices_updater_decode.update(
req_pool_indices,
seq_lens,
seq_lens_sum,
decode_wrappers=decode_wrappers,
encoder_lens=encoder_lens,
spec_info=spec_info,
)
self.decode_cuda_graph_metadata[bs] = decode_wrappers
self.forward_metadata = DecodeMetadata(decode_wrappers)
for i in range(self.num_wrappers):
decode_wrappers[i].begin_forward = partial(
fast_decode_plan, decode_wrappers[i]
)
elif forward_mode.is_target_verify():
prefill_wrappers = []
for i in range(self.num_wrappers):
prefill_wrappers.append(
BatchPrefillWithPagedKVCacheWrapper(
self.workspace_buffer,
"NHD",
use_cuda_graph=True,
qo_indptr_buf=self.cuda_graph_qo_indptr[i][: bs + 1],
paged_kv_indptr_buf=self.kv_indptr[i][: bs + 1],
paged_kv_indices_buf=self.cuda_graph_kv_indices[i],
paged_kv_last_page_len_buf=self.kv_last_page_len[:bs],
custom_mask_buf=self.cuda_graph_custom_mask,
mask_indptr_buf=self.cuda_graph_qk_indptr[i][: bs + 1],
)
)
seq_lens_sum = seq_lens.sum().item()
self.indices_updater_prefill.update(
req_pool_indices,
seq_lens,
seq_lens_sum,
prefix_lens=None,
prefill_wrappers=prefill_wrappers,
use_ragged=False,
encoder_lens=encoder_lens,
spec_info=spec_info,
)
self.prefill_cuda_graph_metadata[bs] = prefill_wrappers
self.forward_metadata = PrefillMetadata(prefill_wrappers, False, False)
else:
raise ValueError(f"Invalid mode: {forward_mode=}")
def init_forward_metadata_replay_cuda_graph(
self,
bs: int,
req_pool_indices: torch.Tensor,
seq_lens: torch.Tensor,
seq_lens_sum: int,
encoder_lens: Optional[torch.Tensor],
forward_mode: ForwardMode,
spec_info: Optional[Union[EagleDraftInput, EagleVerifyInput]],
seq_lens_cpu: Optional[torch.Tensor],
):
if forward_mode.is_decode_or_idle():
self.indices_updater_decode.update(
req_pool_indices[:bs],
seq_lens[:bs],
seq_lens_sum,
decode_wrappers=self.decode_cuda_graph_metadata[bs],
encoder_lens=encoder_lens[:bs] if encoder_lens is not None else None,
spec_info=spec_info,
)
elif forward_mode.is_target_verify():
self.indices_updater_prefill.update(
req_pool_indices[:bs],
seq_lens[:bs],
seq_lens_sum,
prefix_lens=None,
prefill_wrappers=self.prefill_cuda_graph_metadata[bs],
use_ragged=False,
encoder_lens=encoder_lens[:bs] if encoder_lens is not None else None,
spec_info=spec_info,
)
else:
raise ValueError("Invalid forward mode")
def get_cuda_graph_seq_len_fill_value(self):
return 0
def forward_extend(
self,
q: torch.Tensor,
k: torch.Tensor,
v: torch.Tensor,
layer: RadixAttention,
forward_batch: ForwardBatch,
save_kv_cache=True,
):
prefill_wrapper_paged = self.forward_metadata.prefill_wrappers[
self._get_wrapper_idx(layer)
]
cache_loc = (
forward_batch.out_cache_loc
if not layer.is_cross_attention
else forward_batch.encoder_out_cache_loc
)
logits_soft_cap = layer.logit_cap
if not self.forward_metadata.use_ragged:
if k is not None:
assert v is not None
if save_kv_cache:
forward_batch.token_to_kv_pool.set_kv_buffer(
layer, cache_loc, k, v, layer.k_scale, layer.v_scale
)
o = prefill_wrapper_paged.forward(
q.contiguous().view(-1, layer.tp_q_head_num, layer.head_dim),
forward_batch.token_to_kv_pool.get_kv_buffer(layer.layer_id),
causal=not layer.is_cross_attention,
sm_scale=layer.scaling,
window_left=layer.sliding_window_size,
logits_soft_cap=logits_soft_cap,
k_scale=layer.k_scale,
v_scale=layer.v_scale,
)
else:
o1, s1 = self.prefill_wrapper_ragged.forward_return_lse(
q.view(-1, layer.tp_q_head_num, layer.head_dim),
k.view(-1, layer.tp_k_head_num, layer.head_dim),
v.view(-1, layer.tp_v_head_num, layer.head_dim),
causal=True,
sm_scale=layer.scaling,
logits_soft_cap=logits_soft_cap,
)
if self.forward_metadata.extend_no_prefix:
o = o1
else:
o2, s2 = prefill_wrapper_paged.forward_return_lse(
q.contiguous().view(-1, layer.tp_q_head_num, layer.head_dim),
forward_batch.token_to_kv_pool.get_kv_buffer(layer.layer_id),
causal=False,
sm_scale=layer.scaling,
logits_soft_cap=logits_soft_cap,
)
o, _ = merge_state(o1, s1, o2, s2)
if save_kv_cache:
forward_batch.token_to_kv_pool.set_kv_buffer(
layer, cache_loc, k, v, layer.k_scale, layer.v_scale
)
return o.view(-1, layer.tp_q_head_num * layer.head_dim)
def forward_decode(
self,
q: torch.Tensor,
k: torch.Tensor,
v: torch.Tensor,
layer: RadixAttention,
forward_batch: ForwardBatch,
save_kv_cache=True,
):
decode_wrapper = self.forward_metadata.decode_wrappers[
self._get_wrapper_idx(layer)
]
cache_loc = (
forward_batch.out_cache_loc
if not layer.is_cross_attention
else forward_batch.encoder_out_cache_loc
)
if k is not None:
assert v is not None
if save_kv_cache:
forward_batch.token_to_kv_pool.set_kv_buffer(
layer, cache_loc, k, v, layer.k_scale, layer.v_scale
)
o = decode_wrapper.forward(
q.contiguous().view(-1, layer.tp_q_head_num, layer.head_dim),
forward_batch.token_to_kv_pool.get_kv_buffer(layer.layer_id),
sm_scale=layer.scaling,
logits_soft_cap=layer.logit_cap,
k_scale=layer.k_scale,
v_scale=layer.v_scale,
)
return o.view(-1, layer.tp_q_head_num * layer.head_dim)
def _get_wrapper_idx(self, layer: RadixAttention):
if self.num_wrappers == 1:
return 0
if self.dispatch_reason == WrapperDispatch.SLIDING_WINDOW:
return layer.sliding_window_size == -1
if self.dispatch_reason == WrapperDispatch.CROSS_ATTENTION:
return layer.is_cross_attention
raise ValueError(f"Unknown dispatch reason: {self.dispatch_reason}")
class FlashInferIndicesUpdaterDecode:
def __init__(self, model_runner: ModelRunner, attn_backend: AttentionBackend):
# Parse Constants
self.num_qo_heads = (
model_runner.model_config.num_attention_heads // get_attention_tp_size()
)
self.num_kv_heads = model_runner.model_config.get_num_kv_heads(
get_attention_tp_size()
)
self.head_dim = model_runner.model_config.head_dim
self.data_type = model_runner.kv_cache_dtype
self.q_data_type = model_runner.dtype
self.sliding_window_size = model_runner.sliding_window_size
self.attn_backend = attn_backend
# 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
# Dispatch the update function
if self.attn_backend.dispatch_reason == WrapperDispatch.SLIDING_WINDOW:
self.update = self.update_sliding_window
elif self.attn_backend.dispatch_reason == WrapperDispatch.CROSS_ATTENTION:
self.update = self.update_cross_attention
else:
assert self.attn_backend.num_wrappers == 1
self.update = self.update_single_wrapper
def update(
self,
req_pool_indices: torch.Tensor,
seq_lens: torch.Tensor,
seq_lens_sum: int,
decode_wrappers: List[BatchDecodeWithPagedKVCacheWrapper],
encoder_lens: Optional[torch.Tensor],
spec_info: Optional[Union[EagleDraftInput, EagleVerifyInput]],
):
# Keep the signature for type checking. It will be assigned during runtime.
raise NotImplementedError()
def update_single_wrapper(
self,
req_pool_indices: torch.Tensor,
seq_lens: torch.Tensor,
seq_lens_sum: int,
decode_wrappers: List[BatchDecodeWithPagedKVCacheWrapper],
encoder_lens: Optional[torch.Tensor],
spec_info: Optional[Union[EagleDraftInput, EagleVerifyInput]],
):
decode_wrappers = decode_wrappers or self.decode_wrappers
self.call_begin_forward(
decode_wrappers[0],
req_pool_indices,
seq_lens,
seq_lens_sum,
self.kv_indptr[0],
None,
spec_info,
)
def update_sliding_window(
self,
req_pool_indices: torch.Tensor,
seq_lens: torch.Tensor,
seq_lens_sum: int,
decode_wrappers: List[BatchDecodeWithPagedKVCacheWrapper],
encoder_lens: Optional[torch.Tensor],
spec_info: Optional[Union[EagleDraftInput, EagleVerifyInput]],
):
for wrapper_id in range(2):
if wrapper_id == 0:
# Sliding window attention
paged_kernel_lens_tmp = torch.minimum( # TODO: replace this with clamp
seq_lens,
torch.tensor(self.sliding_window_size + 1),
)
paged_kernel_lens_sum_tmp = paged_kernel_lens_tmp.sum().item()
kv_start_idx_tmp = seq_lens - paged_kernel_lens_tmp
else:
# Full attention
paged_kernel_lens_tmp = seq_lens
paged_kernel_lens_sum_tmp = seq_lens_sum
kv_start_idx_tmp = None
self.call_begin_forward(
decode_wrappers[wrapper_id],
req_pool_indices,
paged_kernel_lens_tmp,
paged_kernel_lens_sum_tmp,
self.kv_indptr[wrapper_id],
kv_start_idx_tmp,
spec_info,
)
def update_cross_attention(
self,
req_pool_indices: torch.Tensor,
seq_lens: torch.Tensor,
seq_lens_sum: int,
decode_wrappers: List[BatchDecodeWithPagedKVCacheWrapper],
encoder_lens: Optional[torch.Tensor],
spec_info: Optional[Union[EagleDraftInput, EagleVerifyInput]],
):
for wrapper_id in range(2):
if wrapper_id == 0:
# Normal attention
paged_kernel_lens = seq_lens
kv_start_idx = encoder_lens
else:
# Cross attention
paged_kernel_lens = encoder_lens
kv_start_idx = torch.zeros_like(encoder_lens)
seq_lens_sum = encoder_lens.sum().item()
self.call_begin_forward(
decode_wrappers[wrapper_id],
req_pool_indices,
paged_kernel_lens,
seq_lens_sum,
self.kv_indptr[wrapper_id],
kv_start_idx,
spec_info,
)
def call_begin_forward(
self,
wrapper: BatchDecodeWithPagedKVCacheWrapper,
req_pool_indices: torch.Tensor,
paged_kernel_lens: torch.Tensor,
paged_kernel_lens_sum: int,
kv_indptr: torch.Tensor,
kv_start_idx: torch.Tensor,
spec_info: Optional[Union[EagleDraftInput, EagleVerifyInput]],
):
if spec_info is None:
bs = len(req_pool_indices)
kv_indptr[1 : bs + 1] = torch.cumsum(paged_kernel_lens, dim=0)
kv_indptr = kv_indptr[: bs + 1]
if wrapper.is_cuda_graph_enabled:
# Directly write to the cuda graph input buffer
kv_indices = wrapper._paged_kv_indices_buf
else:
kv_indices = torch.empty(
paged_kernel_lens_sum, dtype=torch.int32, device="cuda"
)
create_flashinfer_kv_indices_triton[(bs,)](
self.req_to_token,
req_pool_indices,
paged_kernel_lens,
kv_indptr,
kv_start_idx,
kv_indices,
self.req_to_token.shape[1],
)
else:
kv_indptr, kv_indices = spec_info.kv_indptr, spec_info.kv_indices
bs = kv_indptr.shape[0] - 1
wrapper.begin_forward(
kv_indptr,
kv_indices,
self.kv_last_page_len[:bs],
self.num_qo_heads,
self.num_kv_heads,
self.head_dim,
1,
data_type=self.data_type,
q_data_type=self.q_data_type,
non_blocking=True,
)
class FlashInferIndicesUpdaterPrefill:
def __init__(self, model_runner: ModelRunner, attn_backend: AttentionBackend):
# Parse Constants
self.num_qo_heads = (
model_runner.model_config.num_attention_heads // get_attention_tp_size()
)
self.num_kv_heads = model_runner.model_config.get_num_kv_heads(
get_attention_tp_size()
)
self.head_dim = model_runner.model_config.head_dim
self.data_type = model_runner.kv_cache_dtype
self.q_data_type = model_runner.dtype
self.sliding_window_size = model_runner.sliding_window_size
self.attn_backend = attn_backend
# 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
# Dispatch the update function
if self.attn_backend.dispatch_reason == WrapperDispatch.SLIDING_WINDOW:
self.update = self.update_sliding_window
elif self.attn_backend.dispatch_reason == WrapperDispatch.CROSS_ATTENTION:
self.update = self.update_cross_attention
else:
assert self.attn_backend.num_wrappers == 1
self.update = self.update_single_wrapper
def update(
self,
req_pool_indices: torch.Tensor,
seq_lens: torch.Tensor,
seq_lens_sum: int,
prefix_lens: torch.Tensor,
prefill_wrappers: List[BatchPrefillWithPagedKVCacheWrapper],
use_ragged: bool,
encoder_lens: Optional[torch.Tensor],
spec_info: Optional[Union[EagleDraftInput, EagleVerifyInput]],
):
# Keep the signature for type checking. It will be assigned during runtime.
raise NotImplementedError()
def update_single_wrapper(
self,
req_pool_indices: torch.Tensor,
seq_lens: torch.Tensor,
seq_lens_sum: int,
prefix_lens: torch.Tensor,
prefill_wrappers: List[BatchPrefillWithPagedKVCacheWrapper],
use_ragged: bool,
encoder_lens: Optional[torch.Tensor],
spec_info: Optional[Union[EagleDraftInput, EagleVerifyInput]],
):
if use_ragged:
paged_kernel_lens = prefix_lens
paged_kernel_lens_sum = paged_kernel_lens.sum().item()
else:
paged_kernel_lens = seq_lens
paged_kernel_lens_sum = seq_lens_sum
self.call_begin_forward(
self.prefill_wrapper_ragged,
prefill_wrappers[0],
req_pool_indices,
paged_kernel_lens,
paged_kernel_lens_sum,
seq_lens,
prefix_lens,
None,
self.kv_indptr[0],
self.qo_indptr[0],
use_ragged,
spec_info,
)
def update_sliding_window(
self,
req_pool_indices: torch.Tensor,
seq_lens: torch.Tensor,
seq_lens_sum: int,
prefix_lens: torch.Tensor,
prefill_wrappers: List[BatchPrefillWithPagedKVCacheWrapper],
use_ragged: bool,
encoder_lens: Optional[torch.Tensor],
spec_info: Optional[Union[EagleDraftInput, EagleVerifyInput]],
):
for wrapper_id in range(2):
if wrapper_id == 0:
# window attention use paged only
paged_kernel_lens = torch.minimum(
seq_lens,
torch.tensor(self.sliding_window_size) + seq_lens - prefix_lens,
)
paged_kernel_lens_sum = paged_kernel_lens.sum().item()
else:
# full attention
paged_kernel_lens = seq_lens
paged_kernel_lens_sum = seq_lens_sum
kv_start_idx = seq_lens - paged_kernel_lens
self.call_begin_forward(
self.prefill_wrapper_ragged,
prefill_wrappers[wrapper_id],
req_pool_indices,
paged_kernel_lens,
paged_kernel_lens_sum,
seq_lens,
prefix_lens,
kv_start_idx,
self.kv_indptr[wrapper_id],
self.qo_indptr[wrapper_id],
use_ragged,
spec_info,
)
def update_cross_attention(
self,
req_pool_indices: torch.Tensor,
seq_lens: torch.Tensor,
seq_lens_sum: int,
prefix_lens: torch.Tensor,
prefill_wrappers: List[BatchPrefillWithPagedKVCacheWrapper],
use_ragged: bool,
encoder_lens: Optional[torch.Tensor],
spec_info: Optional[Union[EagleDraftInput, EagleVerifyInput]],
):
for wrapper_id in range(2):
if wrapper_id == 0:
# normal attention
paged_kernel_lens = seq_lens
kv_start_idx = encoder_lens
paged_kernel_lens_sum = seq_lens_sum
else:
# cross attention
paged_kernel_lens = encoder_lens
kv_start_idx = torch.zeros_like(encoder_lens)
paged_kernel_lens_sum = paged_kernel_lens.sum().item()
self.call_begin_forward(
self.prefill_wrapper_ragged,
prefill_wrappers[wrapper_id],
req_pool_indices,
paged_kernel_lens,
paged_kernel_lens_sum,
seq_lens,
prefix_lens,
kv_start_idx,
self.kv_indptr[wrapper_id],
self.qo_indptr[wrapper_id],
use_ragged,
spec_info,
)
def call_begin_forward(
self,
wrapper_ragged: BatchPrefillWithRaggedKVCacheWrapper,
wrapper_paged: BatchPrefillWithPagedKVCacheWrapper,
req_pool_indices: torch.Tensor,
paged_kernel_lens: torch.Tensor,
paged_kernel_lens_sum: int,
seq_lens: torch.Tensor,
prefix_lens: torch.Tensor,
kv_start_idx: torch.Tensor,
kv_indptr: torch.Tensor,
qo_indptr: torch.Tensor,
use_ragged: bool,
spec_info: Optional[Union[EagleDraftInput, EagleVerifyInput]],
):
bs = len(seq_lens)
if spec_info is None:
assert len(seq_lens) == len(req_pool_indices)
# Normal extend
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 + 256,
dtype=torch.int32,
device=req_pool_indices.device,
)
create_flashinfer_kv_indices_triton[(bs,)](
self.req_to_token,
req_pool_indices,
paged_kernel_lens,
kv_indptr,
kv_start_idx,
kv_indices,
self.req_to_token.shape[1],
)
qo_indptr[1 : bs + 1] = torch.cumsum(seq_lens - prefix_lens, dim=0)
qo_indptr = qo_indptr[: bs + 1]
custom_mask = None
else:
assert isinstance(spec_info, EagleDraftInput) or isinstance(
spec_info, EagleVerifyInput
)
kv_indices, kv_indptr, qo_indptr, custom_mask = (
spec_info.generate_attn_arg_prefill(
req_pool_indices,
paged_kernel_lens,
paged_kernel_lens_sum,
self.req_to_token,
)
)
# extend part
if use_ragged:
wrapper_ragged.begin_forward(
qo_indptr,
qo_indptr,
self.num_qo_heads,
self.num_kv_heads,
self.head_dim,
q_data_type=self.q_data_type,
)
# cached part
wrapper_paged.begin_forward(
qo_indptr,
kv_indptr,
kv_indices,
self.kv_last_page_len[:bs],
self.num_qo_heads,
self.num_kv_heads,
self.head_dim,
1,
q_data_type=self.q_data_type,
kv_data_type=self.data_type,
custom_mask=custom_mask,
non_blocking=True,
)
# Use as a fast path to override the indptr in flashinfer's plan function
# This is used to remove some host-to-device copy overhead.
global global_override_indptr_cpu
class FlashInferMultiStepDraftBackend:
"""
Wrap multiple flashinfer attention backends as one for multiple consecutive
draft decoding steps.
"""
def __init__(
self,
model_runner: ModelRunner,
topk: int,
speculative_num_steps: int,
):
from sglang.srt.speculative.eagle_utils import generate_draft_decode_kv_indices
self.topk = topk
self.speculative_num_steps = speculative_num_steps
self.generate_draft_decode_kv_indices = generate_draft_decode_kv_indices
max_bs = model_runner.req_to_token_pool.size * self.topk
self.kv_indptr = torch.zeros(
(
self.speculative_num_steps,
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.attn_backends = []
for i in range(self.speculative_num_steps):
self.attn_backends.append(
FlashInferAttnBackend(
model_runner,
skip_prefill=True,
kv_indptr_buf=self.kv_indptr[i],
kv_last_page_len_buf=self.kv_last_page_len,
)
)
self.max_context_len = self.attn_backends[0].max_context_len
# Cached variables for generate_draft_decode_kv_indices
self.pool_len = model_runner.req_to_token_pool.req_to_token.shape[1]
def common_template(
self,
forward_batch: ForwardBatch,
kv_indices_buffer: torch.Tensor,
call_fn: Callable,
):
num_seqs = forward_batch.batch_size
bs = self.topk * num_seqs
seq_lens_sum = forward_batch.seq_lens_sum
self.generate_draft_decode_kv_indices[
(self.speculative_num_steps, num_seqs, self.topk)
](
forward_batch.req_pool_indices,
forward_batch.req_to_token_pool.req_to_token,
forward_batch.seq_lens,
kv_indices_buffer,
self.kv_indptr,
forward_batch.positions,
num_seqs,
self.topk,
self.pool_len,
kv_indices_buffer.shape[1],
self.kv_indptr.shape[1],
triton.next_power_of_2(num_seqs),
triton.next_power_of_2(self.speculative_num_steps),
triton.next_power_of_2(bs),
)
assert forward_batch.spec_info is not None
assert isinstance(forward_batch.spec_info, EagleDraftInput)
# Copy the kv_indptr once to avoid multiple device-to-host copies in flashinfer's plan.
indptr_cpu_whole = self.kv_indptr[:, : bs + 1].cpu()
global global_override_indptr_cpu
for i in range(self.speculative_num_steps - 1):
forward_batch.spec_info.kv_indptr = self.kv_indptr[i, : bs + 1]
forward_batch.spec_info.kv_indices = kv_indices_buffer[i][
: seq_lens_sum * self.topk + bs * (i + 1)
]
global_override_indptr_cpu = indptr_cpu_whole[i]
call_fn(i, forward_batch)
global_override_indptr_cpu = None
def init_forward_metadata(self, forward_batch: ForwardBatch):
kv_indices = torch.empty(
(
self.speculative_num_steps,
forward_batch.batch_size * self.topk * self.max_context_len,
),
dtype=torch.int32,
device="cuda",
)
def call_fn(i, forward_batch):
assert forward_batch.spec_info is not None
assert isinstance(forward_batch.spec_info, EagleDraftInput)
forward_batch.spec_info.kv_indptr = (
forward_batch.spec_info.kv_indptr.clone()
)
forward_batch.spec_info.kv_indices = (
forward_batch.spec_info.kv_indices.clone()
)
self.attn_backends[i].init_forward_metadata(forward_batch)
self.common_template(forward_batch, kv_indices, call_fn)
def init_cuda_graph_state(self, max_bs: int):
self.cuda_graph_kv_indices = torch.zeros(
(self.speculative_num_steps, max_bs * self.max_context_len),
dtype=torch.int32,
device="cuda",
)
for i in range(self.speculative_num_steps):
self.attn_backends[i].init_cuda_graph_state(
max_bs, kv_indices_buf=self.cuda_graph_kv_indices[i]
)
def init_forward_metadata_capture_cuda_graph(self, forward_batch: ForwardBatch):
def call_fn(i, forward_batch):
self.attn_backends[i].init_forward_metadata_capture_cuda_graph(
forward_batch.batch_size,
forward_batch.batch_size * self.topk,
forward_batch.req_pool_indices,
forward_batch.seq_lens,
encoder_lens=None,
forward_mode=ForwardMode.DECODE,
spec_info=forward_batch.spec_info,
)
self.common_template(forward_batch, self.cuda_graph_kv_indices, call_fn)
def init_forward_metadata_replay_cuda_graph(
self, forward_batch: ForwardBatch, bs: int
):
def call_fn(i, forward_batch):
self.attn_backends[i].init_forward_metadata_replay_cuda_graph(
bs,
forward_batch.req_pool_indices,
forward_batch.seq_lens,
seq_lens_sum=-1,
encoder_lens=None,
forward_mode=ForwardMode.DECODE,
spec_info=forward_batch.spec_info,
seq_lens_cpu=None,
)
self.common_template(forward_batch, self.cuda_graph_kv_indices, call_fn)
def should_use_tensor_core(
kv_cache_dtype: torch.dtype,
num_attention_heads: int,
num_kv_heads: int,
) -> bool:
"""
Determine whether to use tensor cores for attention computation.
Args:
kv_cache_dtype: Data type of the KV cache
num_attention_heads: Number of attention heads
num_kv_heads: Number of key/value heads
Returns:
bool: Whether to use tensor cores
"""
# Try to use environment variable first
env_override = os.environ.get("SGLANG_FLASHINFER_USE_TENSOR_CORE")
if env_override is not None:
return env_override.lower() == "true"
# Try to use _grouped_size_compiled_for_decode_kernels if available
# This is for flashinfer <=0.1.6. Otherwise, there is an accuracy bug
try:
from flashinfer.decode import _grouped_size_compiled_for_decode_kernels
if not _grouped_size_compiled_for_decode_kernels(
num_attention_heads,
num_kv_heads,
):
return True
else:
return False
except (ImportError, AttributeError):
pass
# Calculate GQA group size
gqa_group_size = num_attention_heads // num_kv_heads
# Determine based on dtype and GQA group size
if kv_cache_dtype in (torch.float8_e4m3fn, torch.float8_e5m2):
return True
elif kv_cache_dtype in (torch.float16, torch.half, torch.bfloat16):
return gqa_group_size > 4
else:
return False
# Use as a fast path to override the indptr in flashinfer's plan function
# This is used to remove some host-to-device copy overhead.
global_override_indptr_cpu = None
def fast_decode_plan(
self,
indptr: torch.Tensor,
indices: torch.Tensor,
last_page_len: torch.Tensor,
num_qo_heads: int,
num_kv_heads: int,
head_dim: int,
page_size: int,
pos_encoding_mode: str = "NONE",
window_left: int = -1,
logits_soft_cap: Optional[float] = None,
data_type: Union[str, torch.dtype] = "float16",
q_data_type: Optional[Union[str, torch.dtype]] = None,
sm_scale: Optional[float] = None,
rope_scale: Optional[float] = None,
rope_theta: Optional[float] = None,
non_blocking: bool = True,
) -> None:
"""
A faster version of BatchDecodeWithPagedKVCacheWrapper::plan used for FlashInferMultiStepDraftBackend.
Modifications:
- Remove unnecessary device-to-device copy for the cuda graph buffers.
- Remove unnecessary host-to-device copy for the metadata buffers.
"""
batch_size = len(last_page_len)
if logits_soft_cap is None:
logits_soft_cap = 0.0
if self.use_tensor_cores:
qo_indptr_host = _get_range_buf(batch_size + 1, "cpu")
if self.is_cuda_graph_enabled:
if batch_size != self._fixed_batch_size:
raise ValueError(
"The batch size should be fixed in cudagraph mode, the runtime batch size {} "
" mismatches the batch size set during initialization {}".format(
batch_size, self._fixed_batch_size
)
)
if len(indices) > len(self._paged_kv_indices_buf):
raise ValueError(
"The size of indices should be less than or equal to the allocated buffer"
)
# Skip these copies because we directly write to them during prepartion
# self._paged_kv_indptr_buf.copy_(indptr)
# self._paged_kv_indices_buf[: len(indices)] = indices
# self._paged_kv_last_page_len_buf.copy_(last_page_len)
else:
self._paged_kv_indptr_buf = indptr
self._paged_kv_indices_buf = indices
self._paged_kv_last_page_len_buf = last_page_len
self._qo_indptr_buf = qo_indptr_host.to(self.device, non_blocking=non_blocking)
# NOTE(Zihao): the following tensors acts as placeholder to pass dtype info
if not q_data_type:
q_data_type = data_type
if not hasattr(self, "empty_q_data"):
self.empty_q_data = torch.empty(
0,
dtype=(
getattr(torch, q_data_type)
if isinstance(q_data_type, str)
else q_data_type
),
)
self.empty_kv_cache = torch.empty(
0,
dtype=(
getattr(torch, data_type) if isinstance(data_type, str) else data_type
),
)
self.last_page_len = torch.ones(32768, dtype=torch.int32)
indptr_host = (
global_override_indptr_cpu
if global_override_indptr_cpu is not None
else indptr.cpu()
)
if self.use_tensor_cores:
kv_lens_arr_host = get_seq_lens(
indptr_host, self.last_page_len[:batch_size], page_size
)
self._plan_info = self._cached_module.plan(
self._float_workspace_buffer,
self._int_workspace_buffer,
self._pin_memory_int_workspace_buffer,
qo_indptr_host,
indptr_host,
kv_lens_arr_host,
batch_size, # total_num_rows
batch_size,
num_qo_heads,
num_kv_heads,
page_size,
self.is_cuda_graph_enabled,
head_dim,
head_dim,
False, # causal
torch.cuda.current_stream().cuda_stream,
)
else:
self._plan_info = self._cached_module.plan(
self._float_workspace_buffer,
self._int_workspace_buffer,
self._pin_memory_int_workspace_buffer,
indptr_host,
batch_size,
num_qo_heads,
num_kv_heads,
page_size,
self.is_cuda_graph_enabled,
window_left,
logits_soft_cap,
head_dim,
head_dim,
self.empty_q_data,
self.empty_kv_cache,
torch.cuda.current_stream().cuda_stream,
)
self._pos_encoding_mode = pos_encoding_mode
self._window_left = window_left
self._logits_soft_cap = logits_soft_cap
self._sm_scale = sm_scale
self._rope_scale = rope_scale
self._rope_theta = rope_theta