rocksdb/util/threadpool.h

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// Copyright (c) 2011-present, Facebook, Inc. All rights reserved.
// This source code is licensed under the BSD-style license found in the
// LICENSE file in the root directory of this source tree. An additional grant
// of patent rights can be found in the PATENTS file in the same directory.
//
// Copyright (c) 2011 The LevelDB Authors. All rights reserved.
// Use of this source code is governed by a BSD-style license that can be
// found in the LICENSE file. See the AUTHORS file for names of contributors.
#pragma once
#ifdef OS_WIN
# define ROCKSDB_STD_THREADPOOL
#endif
#include "rocksdb/env.h"
#include "util/thread_status_util.h"
#ifdef ROCKSDB_STD_THREADPOOL
# include <thread>
# include <mutex>
# include <condition_variable>
#endif
#include <atomic>
#include <vector>
namespace rocksdb {
class ThreadPool {
public:
ThreadPool();
~ThreadPool();
void JoinAllThreads();
void LowerIOPriority();
void BGThread(size_t thread_id);
void WakeUpAllThreads();
void IncBackgroundThreadsIfNeeded(int num);
void SetBackgroundThreads(int num);
void StartBGThreads();
void Schedule(void (*function)(void* arg1), void* arg, void* tag,
void (*unschedFunction)(void* arg));
int UnSchedule(void* arg);
unsigned int GetQueueLen() const {
return queue_len_.load(std::memory_order_relaxed);
}
void SetHostEnv(Env* env) { env_ = env; }
Env* GetHostEnv() const { return env_; }
// Return true if there is at least one thread needs to terminate.
bool HasExcessiveThread() const {
return static_cast<int>(bgthreads_.size()) > total_threads_limit_;
}
// Return true iff the current thread is the excessive thread to terminate.
// Always terminate the running thread that is added last, even if there are
// more than one thread to terminate.
bool IsLastExcessiveThread(size_t thread_id) const {
return HasExcessiveThread() && thread_id == bgthreads_.size() - 1;
}
// Is one of the threads to terminate.
bool IsExcessiveThread(size_t thread_id) const {
return static_cast<int>(thread_id) >= total_threads_limit_;
}
// Return the thread priority.
// This would allow its member-thread to know its priority.
Env::Priority GetThreadPriority() const { return priority_; }
// Set the thread priority.
void SetThreadPriority(Env::Priority priority) { priority_ = priority; }
static void PthreadCall(const char* label, int result);
private:
// Entry per Schedule() call
struct BGItem {
void* arg;
void (*function)(void*);
void* tag;
void (*unschedFunction)(void*);
};
typedef std::deque<BGItem> BGQueue;
int total_threads_limit_;
#ifdef ROCKSDB_STD_THREADPOOL
std::mutex mu_;
std::condition_variable bgsignal_;
std::vector<std::thread> bgthreads_;
#else
pthread_mutex_t mu_;
pthread_cond_t bgsignal_;
std::vector<pthread_t> bgthreads_;
#endif
BGQueue queue_;
std::atomic_uint queue_len_; // Queue length. Used for stats reporting
bool exit_all_threads_;
bool low_io_priority_;
Env::Priority priority_;
Env* env_;
void SetBackgroundThreadsInternal(int num, bool allow_reduce);
};
} // namespace rocksdb