mirror of https://github.com/gabime/spdlog.git
new approach to async: use thread pool to consume the queues.
davide
9 years ago
parent
c69df8ae44
commit
f8ad4db8ae
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#ifndef THREAD_POOL_H
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#define THREAD_POOL_H
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#include <vector>
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#include <deque>
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#include <memory>
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#include <thread>
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#include <mutex>
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#include <future>
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#include <functional>
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#include <stdexcept>
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#include <assert.h>
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typedef std::function<bool(void)> Func;
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typedef std::shared_ptr<Func> shared_function_ptr;
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typedef std::weak_ptr<Func> weak_function_ptr;
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namespace spdlog
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{
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namespace details
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{
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class thread_pool {
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public:
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thread_pool(size_t num_threads,
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const std::function<void()>& worker_warmup_cb = nullptr,
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const std::function<void()>& worker_teardown_cb = nullptr);
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void subscribe_handle(const shared_function_ptr& loop_handle );
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~thread_pool();
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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::deque< weak_function_ptr > _loop_handles;
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std::deque< bool > _busy;
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// synchronization
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std::mutex _mutex;
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std::function<void()> _worker_warmup_cb;
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std::function<void()> _worker_teardown_cb;
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size_t _index;
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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 thread_pool::thread_pool(size_t num_threads,
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const std::function<void()>& worker_warmup_cb,
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const std::function<void()>& worker_teardown_cb):
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_worker_warmup_cb(worker_warmup_cb),
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_worker_teardown_cb(worker_teardown_cb),
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_index(0),
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_stop(false)
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{
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assert(num_threads > 0);
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for(size_t i = 0;i<num_threads;++i)
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_workers.emplace_back( [this]()
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{
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if( _worker_warmup_cb) _worker_warmup_cb();
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while( !_stop)
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{
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if( _loop_handles.empty()){
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std::this_thread::sleep_for( std::chrono::microseconds(100) );
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}
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else
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{
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shared_function_ptr loop;
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size_t index = 0;
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bool busy = false;
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{
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std::unique_lock<std::mutex> lock(_mutex);
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// scan the _loop_handles to find an available one.
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for (size_t count=0; count<_loop_handles.size(); count++)
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{
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_index = (_index+1) % _loop_handles.size();
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loop = _loop_handles[index].lock();
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busy = _busy[index];
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// if the weak pointer points to a delated handle, remove it
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if(!loop ){
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_loop_handles.erase( _loop_handles.begin() + index);
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_busy.erase ( _busy.begin() + index);
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}
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else{
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_busy[index] = true;
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}
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if( loop && !busy) break;
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}
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}
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if(loop && !busy)
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{
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bool continue_loop = (*loop)();
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if(!continue_loop){
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_loop_handles.erase( _loop_handles.begin() + index);
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_busy.erase ( _busy.begin() + index);
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}
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else{
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std::unique_lock<std::mutex> lock(_mutex);
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_busy[index] = false;
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}
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}
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else{
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// this happens if we haven't find any handle that needs our work
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std::this_thread::sleep_for( std::chrono::milliseconds(1) );
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}
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}
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}
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if( _worker_teardown_cb) _worker_teardown_cb();
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}
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);
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}
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inline void thread_pool::subscribe_handle(const shared_function_ptr &loop_handle)
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{
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std::unique_lock<std::mutex> lock(_mutex);
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_loop_handles.push_back( loop_handle );
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_busy.push_back( false );
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assert( _loop_handles.size() == 1);
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}
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// the destructor joins all threads
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inline thread_pool::~thread_pool()
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{
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{
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std::unique_lock<std::mutex> lock(_mutex);
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_stop = true;
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}
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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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}
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#endif
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