Revert "[PerfFix] Avoid separate thread for MP executor shm spin (#28012)" (#28289)

Signed-off-by: NickLucche <nlucches@redhat.com>

Author: NickLucche

tests/v1/executor/test_executor.py

@@ -4,7 +4,6 @@
 import asyncio
 import os
 from collections.abc import Callable
-from concurrent.futures import Future
 from typing import Any
 
 import pytest
@@ -28,7 +27,7 @@ def collective_rpc(
         kwargs: dict | None = None,
         non_block: bool = False,
         unique_reply_rank: int | None = None,
-    ) -> Any | list[Any] | Future[Any | list[Any]]:
+    ) -> list[Any]:
         # Drop marker to show that this was run
         with open(".marker", "w"):
             ...

tests/v1/kv_connector/unit/test_output_aggregator.py

@@ -89,12 +89,14 @@ def test_aggregate_workers_output():
 def test_async_aggregate_workers_output():
     aggregator = KVOutputAggregator(expected_finished_count=2)
 
-    future: Future[list[DummyModelRunnerOutput]] = Future()
-    result_future = aggregator.async_aggregate(future)
+    future1: Future[DummyModelRunnerOutput] = Future()
+    future2: Future[DummyModelRunnerOutput] = Future()
+    result_future = aggregator.async_aggregate([future1, future2])
 
     output1 = DummyModelRunnerOutput()
     output2 = DummyModelRunnerOutput()
-    future.set_result([output1, output2])
+    future1.set_result(output1)
+    future2.set_result(output2)
 
     assert result_future.done()
     aggregated = result_future.result()
@@ -104,14 +106,16 @@ def test_async_aggregate_workers_output():
     assert aggregated.finished_recving is None
     assert not aggregated.invalid_block_ids
 
-    future = Future()
-    result_future = aggregator.async_aggregate(future)
+    future1 = Future()
+    future2 = Future()
+    result_future = aggregator.async_aggregate([future1, future2])
 
     output1 = DummyModelRunnerOutput(
         finished_sending={"req1"}, finished_recving={"req2"}
     )
     output2 = DummyModelRunnerOutput(invalid_block_ids={1})
-    future.set_result([output1, output2])
+    future1.set_result(output1)
+    future2.set_result(output2)
 
     assert result_future.done()
     aggregated = result_future.result()
@@ -121,12 +125,14 @@ def test_async_aggregate_workers_output():
     assert aggregated.finished_recving is None
     assert aggregated.invalid_block_ids == {1}
 
-    future = Future()
-    result_future = aggregator.async_aggregate(future)
+    future1 = Future()
+    future2 = Future()
+    result_future = aggregator.async_aggregate([future1, future2])
 
     output1 = DummyModelRunnerOutput(invalid_block_ids={2})
     output2 = DummyModelRunnerOutput(finished_sending={"req1"})
-    future.set_result([output1, output2])
+    future1.set_result(output1)
+    future2.set_result(output2)
 
     assert result_future.done()
     aggregated = result_future.result()
@@ -136,14 +142,16 @@ def test_async_aggregate_workers_output():
     assert aggregated.finished_recving is None
     assert aggregated.invalid_block_ids == {2}
 
-    future = Future()
-    result_future = aggregator.async_aggregate(future)
+    future1 = Future()
+    future2 = Future()
+    result_future = aggregator.async_aggregate([future1, future2])
 
     output1 = DummyModelRunnerOutput(invalid_block_ids={3, 4})
     output2 = DummyModelRunnerOutput(
         finished_recving={"req2"}, invalid_block_ids={4, 5}
     )
-    future.set_result([output1, output2])
+    future1.set_result(output1)
+    future2.set_result(output2)
 
     assert result_future.done()
     aggregated = result_future.result()

vllm/distributed/kv_transfer/kv_connector/utils.py

@@ -221,24 +221,39 @@ def update_finished_set(
 
     def async_aggregate(
         self,
-        output_future: Future[Sequence[ModelRunnerOutput | None]],
+        output_futures: Sequence[Future[ModelRunnerOutput | None]],
         output_rank: int = 0,
     ) -> Future[ModelRunnerOutput | None]:
-        """Takes a future that resolves to a list of outputs and returns a future
-        which resolves to a single aggregated output."""
+        """Takes a list of futures and returns a single future which resolves
+        to the respective list of outputs."""
         result_future: Future[ModelRunnerOutput | None] = Future()
 
-        def callback(fut):
-            if result_future.done():
-                return
-            try:
-                result_future.set_result(self.aggregate(fut.result(), output_rank))
-            except CancelledError:
-                result_future.cancel()
-            except Exception as e:
-                result_future.set_exception(e)
-
-        output_future.add_done_callback(callback)
+        outputs: list[ModelRunnerOutput | None] = [None] * len(output_futures)
+        remaining = len(output_futures)
+
+        def make_callback(idx):
+            def callback(fut):
+                if result_future.done():
+                    return
+
+                try:
+                    outputs[idx] = fut.result()
+                except CancelledError:
+                    result_future.cancel()
+                except Exception as e:
+                    result_future.set_exception(e)
+
+                # this check assumes io_thread_pool uses a single thread
+                nonlocal remaining
+                remaining -= 1
+                if not remaining:
+                    result_future.set_result(self.aggregate(outputs, output_rank))
+
+            return callback
+
+        for i, output_future in enumerate(output_futures):
+            output_future.add_done_callback(make_callback(i))
+
         return result_future
 
 

vllm/v1/executor/abstract.py

@@ -171,7 +171,7 @@ def collective_rpc(
         args: tuple = (),
         kwargs: dict | None = None,
         non_block: Literal[True] = True,
-    ) -> Future[list[_R]]:
+    ) -> list[Future[_R]]:
         pass
 
     @abstractmethod
@@ -219,7 +219,7 @@ def sample_tokens(
 
     def sample_tokens(
         self, grammar_output: GrammarOutput | None, non_block: bool = False
-    ) -> ModelRunnerOutput | None | Future[ModelRunnerOutput | None]:
+    ) -> ModelRunnerOutput | Future[ModelRunnerOutput]:
         output = self.collective_rpc(  # type: ignore[call-overload]
             "sample_tokens", args=(grammar_output,), non_block=non_block
         )

vllm/v1/executor/multiproc_executor.py

@@ -9,10 +9,8 @@
 import time
 import traceback
 import weakref
-from collections import deque
 from collections.abc import Callable
-from concurrent.futures import Future, InvalidStateError
-from contextlib import suppress
+from concurrent.futures import Future, ThreadPoolExecutor
 from dataclasses import dataclass
 from enum import Enum, auto
 from functools import cached_property, partial
@@ -56,30 +54,6 @@
 logger = init_logger(__name__)
 
 
-class FutureWrapper(Future):
-    def __init__(self, futures_queue: deque[tuple["FutureWrapper", Callable]]):
-        self.futures_queue = futures_queue
-        super().__init__()
-
-    def result(self, timeout=None):
-        if timeout is not None:
-            raise RuntimeError("timeout not implemented")
-        # Drain any futures ahead of us in the queue.
-        while not self.done():
-            future, get_response = self.futures_queue.pop()
-            future.wait_for_response(get_response)
-        return super().result()
-
-    def wait_for_response(self, get_response: Callable):
-        try:
-            response = get_response()
-            with suppress(InvalidStateError):
-                self.set_result(response)
-        except Exception as e:
-            with suppress(InvalidStateError):
-                self.set_exception(e)
-
-
 class MultiprocExecutor(Executor):
     supports_pp: bool = True
 
@@ -90,6 +64,7 @@ def _init_executor(self) -> None:
         self.is_failed = False
         self.shutdown_event = threading.Event()
         self.failure_callback: FailureCallback | None = None
+        self.io_thread_pool: ThreadPoolExecutor | None = None
 
         self.world_size = self.parallel_config.world_size
         tensor_parallel_size = self.parallel_config.tensor_parallel_size
@@ -157,7 +132,12 @@ def _init_executor(self) -> None:
                         uw.death_writer.close()
                 self._ensure_worker_termination([uw.proc for uw in unready_workers])
 
-        self.futures_queue = deque[tuple[FutureWrapper, Callable]]()
+        # Note: must use only 1 IO thread to keep dequeue sequence
+        # from the response queue.
+        # _async_aggregate_workers_output also assumes a single IO thread.
+        self.io_thread_pool = ThreadPoolExecutor(
+            max_workers=1, thread_name_prefix="mp_exec_io"
+        )
 
         self.output_rank = self._get_output_rank()
         self.has_connector = self.vllm_config.kv_transfer_config is not None
@@ -215,13 +195,14 @@ def _execute_with_aggregation(
     ) -> ModelRunnerOutput | None | Future[ModelRunnerOutput | None]:
         if not self.has_connector:
             # get output only from a single worker (output_rank)
-            return self.collective_rpc(
+            (output,) = self.collective_rpc(
                 method,
                 args=args,
                 unique_reply_rank=self.output_rank,
                 non_block=non_block,
                 timeout=envs.VLLM_EXECUTE_MODEL_TIMEOUT_SECONDS,
             )
+            return output
 
         # get output from all workers
         outputs = self.collective_rpc(
@@ -242,21 +223,20 @@ def execute_dummy_batch(self) -> None:
 
     def take_draft_token_ids(self) -> DraftTokenIds | None:
         # OPTIMIZATION: Get output only from a single worker (output_rank)
-        return self.collective_rpc(
+        outputs = self.collective_rpc(
             "take_draft_token_ids", unique_reply_rank=self.output_rank
         )
+        return outputs[0]
 
-    def collective_rpc(  # type: ignore[override]
+    def collective_rpc(
         self,
         method: str | Callable,
         timeout: float | None = None,
         args: tuple = (),
         kwargs: dict | None = None,
         non_block: bool = False,
         unique_reply_rank: int | None = None,
-    ) -> Any | list[Any] | Future[Any | list[Any]]:
-        """Returns single result if unique_reply_rank is provided, otherwise list."""
-
+    ) -> list[Any]:
         if self.is_failed:
             raise RuntimeError("Executor failed.")
 
@@ -266,52 +246,63 @@ def collective_rpc(  # type: ignore[override]
         # NOTE: If the args are heterogeneous, then we pack them into a list,
         # and unpack them in the method of every worker, because every worker
         # knows their own rank.
+        try:
+            if isinstance(method, str):
+                send_method = method
+            else:
+                send_method = cloudpickle.dumps(
+                    method, protocol=pickle.HIGHEST_PROTOCOL
+                )
+            self.rpc_broadcast_mq.enqueue(
+                (send_method, args, kwargs, unique_reply_rank)
+            )
 
-        if isinstance(method, str):
-            send_method = method
-        else:
-            send_method = cloudpickle.dumps(method, protocol=pickle.HIGHEST_PROTOCOL)
-        self.rpc_broadcast_mq.enqueue((send_method, args, kwargs, unique_reply_rank))
+            workers = (
+                (self.workers[unique_reply_rank],)
+                if unique_reply_rank is not None
+                else self.workers
+            )
+            responses = []
 
-        workers = (
-            (self.workers[unique_reply_rank],)
-            if unique_reply_rank is not None
-            else self.workers
-        )
+            def get_response(
+                w: WorkerProcHandle,
+                dequeue_timeout: float | None = None,
+                cancel_event: threading.Event | None = None,
+            ):
+                status, result = w.worker_response_mq.dequeue(
+                    timeout=dequeue_timeout, cancel=cancel_event
+                )
 
-        shutdown_event = self.shutdown_event
+                if status != WorkerProc.ResponseStatus.SUCCESS:
+                    raise RuntimeError(
+                        f"Worker failed with error '{result}', please check the"
+                        " stack trace above for the root cause"
+                    )
+                return result
 
-        def get_response():
-            responses = []
             for w in workers:
                 dequeue_timeout = (
                     None if deadline is None else (deadline - time.monotonic())
                 )
-                try:
-                    status, result = w.worker_response_mq.dequeue(
-                        timeout=dequeue_timeout, cancel=shutdown_event
+
+                if self.io_thread_pool is not None:
+                    # We must consume worker_response_mq from a single thread.
+                    result = self.io_thread_pool.submit(  # type: ignore
+                        get_response, w, dequeue_timeout, self.shutdown_event
                     )
-                except TimeoutError as e:
-                    raise TimeoutError(f"RPC call to {method} timed out.") from e
-                if status != WorkerProc.ResponseStatus.SUCCESS:
+                    if not non_block:
+                        result = result.result()
+                elif not non_block:
+                    result = get_response(w, dequeue_timeout, self.shutdown_event)
+                else:
                     raise RuntimeError(
-                        f"Worker failed with error '{result}', please check the"
-                        " stack trace above for the root cause"
+                        "non_block can only be used when max_concurrent_batches > 1"
                     )
                 responses.append(result)
-            return responses[0] if unique_reply_rank is not None else responses
-
-        if non_block:
-            future = FutureWrapper(self.futures_queue)
-            self.futures_queue.appendleft((future, get_response))
-            return future
-
-        # First drain any pending futures in the queue.
-        while self.futures_queue:
-            future, get_fut_response = self.futures_queue.pop()
-            future.wait_for_response(get_fut_response)
 
-        return get_response()
+            return responses
+        except TimeoutError as e:
+            raise TimeoutError(f"RPC call to {method} timed out.") from e
 
     @staticmethod
     def _ensure_worker_termination(worker_procs: list[BaseProcess]):
@@ -357,6 +348,9 @@ def shutdown(self):
                 self._ensure_worker_termination([w.proc for w in workers])
 
             self.shutdown_event.set()
+            if self.io_thread_pool is not None:
+                self.io_thread_pool.shutdown(wait=False, cancel_futures=True)
+                del self.io_thread_pool
 
         self.rpc_broadcast_mq = None