129 lines
4.4 KiB
Python
129 lines
4.4 KiB
Python
# SPDX-License-Identifier: Apache-2.0
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# SPDX-FileCopyrightText: Copyright contributors to the vLLM project
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from collections.abc import Callable
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from enum import Enum
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from typing import Any
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import torch
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class AuxStreamType(Enum):
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Attention = 1
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class EventType(Enum):
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Main = 0
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Attention = 1
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def maybe_execute_in_parallel(
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fn0: Callable[[], Any],
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fn1: Callable[[], Any],
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event0: torch.cuda.Event,
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event1: torch.cuda.Event,
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aux_stream: torch.cuda.Stream | None = None,
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) -> tuple[Any, Any]:
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"""Run two functions potentially in parallel on separate CUDA streams.
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When aux_stream is provided, fn0 runs on the current (default) stream and
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fn1 runs on aux_stream, synchronized via CUDA events. When aux_stream is
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None, both functions execute sequentially on the current stream.
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This design follows TensorRT-LLM's maybe_execute_in_parallel pattern
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(tensorrt_llm/_torch/modules/multi_stream_utils.py).
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Args:
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fn0: Callable for the default stream.
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fn1: Callable for the auxiliary stream.
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event0: CUDA event recorded before fn0 so aux_stream can wait.
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event1: CUDA event recorded after fn1 so default stream can wait.
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aux_stream: The second CUDA stream for fn1.
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Multi-stream is disabled when aux_stream is None.
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Returns:
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Tuple of (fn0_result, fn1_result).
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"""
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if aux_stream is not None:
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event0.record()
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result0 = fn0()
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with torch.cuda.stream(aux_stream):
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event0.wait()
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result1 = fn1()
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event1.record()
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event1.wait()
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else:
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result0 = fn0()
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result1 = fn1()
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return (result0, result1)
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def execute_in_parallel(
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default_fn: Callable[[], Any],
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aux_fns: list[Callable[[], Any] | None],
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start_event: torch.cuda.Event,
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done_events: list[torch.cuda.Event],
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aux_streams: list[torch.cuda.Stream] | None = None,
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enable: bool = False,
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) -> tuple[Any, list[Any]]:
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"""Run default_fn on the current stream and aux_fns concurrently on
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aux_streams.
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Generalizes maybe_execute_in_parallel to N aux callables. Slots where
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aux_fns[i] is None are skipped (no stream switch, no event record); their
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corresponding entry in the returned aux_results list is None.
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start_event fans out from the current stream to every launched aux stream;
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done_events[i] is recorded after aux_fns[i] so the current stream joins
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before returning. Falls back to sequential execution on the current stream
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when aux_streams is None or enable is False; in that case default_fn runs
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first, then aux_fns in order.
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Args:
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default_fn: Callable for the default (current) stream.
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aux_fns: Per-aux callables; entries may be None to skip.
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start_event: CUDA event recorded on the current stream before
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default_fn so each launched aux stream can wait on it.
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done_events: One CUDA event per aux slot, recorded after the
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corresponding aux_fn. Length must match aux_fns.
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aux_streams: Per-aux CUDA streams. Length must match aux_fns.
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Multi-stream is disabled when None.
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enable: Opt-in switch for the multi-stream path. Defaults to False,
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so callers that pass aux_streams must also pass enable=True
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(typically gated by an env var) to actually overlap. When False,
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execution falls back to sequential on the current stream.
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Returns:
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Tuple of (default_result, aux_results) where aux_results[i] is the
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result of aux_fns[i] (or None when skipped).
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"""
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aux_results: list[Any]
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if aux_streams is None or not enable:
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default_result = default_fn()
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aux_results = [fn() if fn is not None else None for fn in aux_fns]
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return default_result, aux_results
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assert len(aux_fns) == len(aux_streams) == len(done_events), (
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"aux_fns, aux_streams, and done_events must be the same length"
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)
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aux_results = [None] * len(aux_fns)
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pending: list[torch.cuda.Event] = []
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start_event.record()
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for i, fn in enumerate(aux_fns):
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if fn is None:
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continue
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with torch.cuda.stream(aux_streams[i]):
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start_event.wait()
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aux_results[i] = fn()
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done_events[i].record()
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pending.append(done_events[i])
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default_result = default_fn()
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for ev in pending:
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ev.wait()
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return default_result, aux_results
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