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vLLM/vllm/v1/worker/ubatch_utils.py
T
2025-12-16 00:04:01 -05:00

113 lines
3.6 KiB
Python

# SPDX-License-Identifier: Apache-2.0
# SPDX-FileCopyrightText: Copyright contributors to the vLLM project
from dataclasses import dataclass
from typing import TypeAlias
import numpy as np
from vllm.config import ParallelConfig
@dataclass
class UBatchSlice:
request_slice: slice
token_slice: slice
def is_empty(self) -> bool:
return (
self.request_slice.start == self.request_slice.stop
or self.token_slice.start == self.token_slice.stop
)
@property
def num_tokens(self) -> int:
return self.token_slice.stop - self.token_slice.start
UBatchSlices: TypeAlias = list[UBatchSlice]
def is_last_ubatch_empty(
orig_num_tokens: int, padded_num_tokens: int, num_ubatches: int
) -> bool:
return (padded_num_tokens // num_ubatches) * (num_ubatches - 1) >= orig_num_tokens
def check_ubatch_thresholds(
config: ParallelConfig, num_tokens: int, uniform_decode: bool
) -> bool:
if not config.use_ubatching:
return False
if uniform_decode:
return num_tokens >= config.dbo_decode_token_threshold
else:
return num_tokens >= config.dbo_prefill_token_threshold
# This pads the last ubatch slice out to the total number of tokens
# (num_tokens + padding) since we do `create_ubatch_slices` before applying DP padding.
def _pad_out_ubatch_slices(
ubatch_slices: UBatchSlices, num_total_tokens: int, num_reqs_padded: int
) -> UBatchSlices:
last_slice = ubatch_slices[-1]
padded_last_request_slice = slice(last_slice.request_slice.start, num_reqs_padded)
padded_last_token_slice = slice(last_slice.token_slice.start, num_total_tokens)
return ubatch_slices[:-1] + [
UBatchSlice(padded_last_request_slice, padded_last_token_slice)
]
def maybe_create_ubatch_slices(
should_ubatch: bool,
num_scheduled_tokens: np.ndarray,
num_tokens_padded: int,
num_reqs_padded: int,
num_ubatches: int,
split_point: list[int] | int | None = None,
) -> tuple[UBatchSlices | None, UBatchSlices | None]:
if not should_ubatch:
return None, None
if split_point is None:
split_point = int(num_tokens_padded) // num_ubatches
token_split_points = [split_point * i for i in range(1, num_ubatches)]
# TODO(lucas): Refactor the gpu_model_runner.py so we can pass
# in cu_num_tokens directly (i.e. query_start_loc)
cu_num_tokens = np.zeros(len(num_scheduled_tokens) + 1, dtype=np.int32)
np.cumsum(num_scheduled_tokens, dtype=np.int32, out=cu_num_tokens[1:])
ubatch_slices = []
start_token = 0
# Add the end point to the split points to make iteration easier
all_points = token_split_points + [cu_num_tokens[-1]]
for end_token in all_points:
token_slice = slice(start_token, end_token)
# Determine request slices using exclusive stop semantics
# Ubatch includes requests whose tokens overlap [start_token, end_token)
# Start at the request that contains the start_token
# or the request starting exactly at start_token (if on boundary)
req_start = int(np.searchsorted(cu_num_tokens, start_token, side="right") - 1)
# Stop at the request that starts at or after end_token
req_stop = int(np.searchsorted(cu_num_tokens, end_token, side="left"))
req_slice = slice(req_start, req_stop)
ubatch_slices.append(UBatchSlice(req_slice, token_slice))
start_token = end_token
ubatch_slices_padded = _pad_out_ubatch_slices(
ubatch_slices, num_tokens_padded, num_reqs_padded
)
assert sum(s.num_tokens for s in ubatch_slices_padded) == num_tokens_padded
return ubatch_slices, ubatch_slices_padded