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107 lines
3.1 KiB
C++
107 lines
3.1 KiB
C++
// https://github.com/jhasse/ThreadPool
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#pragma once
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#include <functional>
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#include <future>
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#include <queue>
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#include "logger.h"
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class ThreadPool {
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public:
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explicit ThreadPool(size_t);
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template<class F, class... Args>
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decltype(auto) enqueue(F&& f, Args&&... args);
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void log_exhaustion();
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void shutdown();
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private:
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// need to keep track of threads so we can join them
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std::vector< std::thread > workers;
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// the task queue
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std::queue< std::packaged_task<void()> > tasks;
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// synchronization
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std::mutex queue_mutex;
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std::condition_variable condition;
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std::condition_variable condition_producers;
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bool stop;
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};
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// the constructor just launches some amount of workers
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inline ThreadPool::ThreadPool(size_t threads)
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: stop(false)
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{
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for(size_t i = 0;i<threads;++i)
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workers.emplace_back(
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[this]
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{
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for(;;)
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{
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std::packaged_task<void()> task;
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{
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std::unique_lock<std::mutex> lock(this->queue_mutex);
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this->condition.wait(lock,
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[this]{ return this->stop || !this->tasks.empty(); });
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if(this->stop) {
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return;
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}
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if(this->tasks.empty()) {
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continue;
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}
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task = std::move(this->tasks.front());
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this->tasks.pop();
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if (tasks.empty()) {
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condition_producers.notify_one(); // notify the destructor that the queue is empty
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}
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}
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task();
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}
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}
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);
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}
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// add new work item to the pool
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template<class F, class... Args>
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decltype(auto) ThreadPool::enqueue(F&& f, Args&&... args)
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{
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using return_type = std::invoke_result_t<F, Args...>;
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std::packaged_task<return_type()> task(
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std::bind(std::forward<F>(f), std::forward<Args>(args)...)
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);
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std::future<return_type> res = task.get_future();
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{
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std::unique_lock<std::mutex> lock(queue_mutex);
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// don't allow enqueueing after stopping the pool
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if(!stop) {
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tasks.emplace(std::move(task));
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}
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}
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condition.notify_one();
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return res;
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}
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inline void ThreadPool::shutdown() {
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{
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std::unique_lock<std::mutex> lock(queue_mutex);
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condition_producers.wait(lock, [this] { return tasks.empty(); });
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stop = true;
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}
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condition.notify_all();
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for (std::thread& worker : workers) {
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worker.join();
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}
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}
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inline void ThreadPool::log_exhaustion() {
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std::unique_lock<std::mutex> lock(queue_mutex);
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if(tasks.size() >= workers.size()) {
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LOG(WARNING) << "Threadpool exhaustion detected, task_queue_len: "
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<< tasks.size() << ", thread_pool_len: " << workers.size();
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}
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}
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