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- /*
- * Copyright 2017-present Facebook, Inc.
- *
- * Licensed under the Apache License, Version 2.0 (the "License");
- * you may not use this file except in compliance with the License.
- * You may obtain a copy of the License at
- *
- * http://www.apache.org/licenses/LICENSE-2.0
- *
- * Unless required by applicable law or agreed to in writing, software
- * distributed under the License is distributed on an "AS IS" BASIS,
- * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
- * See the License for the specific language governing permissions and
- * limitations under the License.
- */
- #pragma once
- #include <atomic>
- #include <folly/executors/IOExecutor.h>
- #include <folly/executors/ThreadPoolExecutor.h>
- #include <folly/io/async/EventBaseManager.h>
- namespace folly {
- /**
- * A Thread Pool for IO bound tasks
- *
- * @note Uses event_fd for notification, and waking an epoll loop.
- * There is one queue (NotificationQueue specifically) per thread/epoll.
- * If the thread is already running and not waiting on epoll,
- * we don't make any additional syscalls to wake up the loop,
- * just put the new task in the queue.
- * If any thread has been waiting for more than a few seconds,
- * its stack is madvised away. Currently however tasks are scheduled round
- * robin on the queues, so unless there is no work going on,
- * this isn't very effective.
- * Since there is one queue per thread, there is hardly any contention
- * on the queues - so a simple spinlock around an std::deque is used for
- * the tasks. There is no max queue size.
- * By default, there is one thread per core - it usually doesn't make sense to
- * have more IO threads than this, assuming they don't block.
- *
- * @note ::getEventBase() will return an EventBase you can schedule IO work on
- * directly, chosen round-robin.
- *
- * @note N.B. For this thread pool, stop() behaves like join() because
- * outstanding tasks belong to the event base and will be executed upon its
- * destruction.
- */
- class IOThreadPoolExecutor : public ThreadPoolExecutor, public IOExecutor {
- public:
- explicit IOThreadPoolExecutor(
- size_t numThreads,
- std::shared_ptr<ThreadFactory> threadFactory =
- std::make_shared<NamedThreadFactory>("IOThreadPool"),
- folly::EventBaseManager* ebm = folly::EventBaseManager::get(),
- bool waitForAll = false);
- ~IOThreadPoolExecutor() override;
- void add(Func func) override;
- void add(
- Func func,
- std::chrono::milliseconds expiration,
- Func expireCallback = nullptr) override;
- folly::EventBase* getEventBase() override;
- static folly::EventBase* getEventBase(ThreadPoolExecutor::ThreadHandle*);
- folly::EventBaseManager* getEventBaseManager();
- private:
- struct alignas(hardware_destructive_interference_size) IOThread
- : public Thread {
- IOThread(IOThreadPoolExecutor* pool)
- : Thread(pool), shouldRun(true), pendingTasks(0) {}
- std::atomic<bool> shouldRun;
- std::atomic<size_t> pendingTasks;
- folly::EventBase* eventBase;
- std::mutex eventBaseShutdownMutex_;
- };
- ThreadPtr makeThread() override;
- std::shared_ptr<IOThread> pickThread();
- void threadRun(ThreadPtr thread) override;
- void stopThreads(size_t n) override;
- size_t getPendingTaskCountImpl() override;
- std::atomic<size_t> nextThread_;
- folly::ThreadLocal<std::shared_ptr<IOThread>> thisThread_;
- folly::EventBaseManager* eventBaseManager_;
- };
- } // namespace folly
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