Siying Dong
9 years ago
commit
9c227923c6
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// Copyright (c) 2013, Facebook, Inc. All rights reserved.
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// This source code is licensed under the BSD-style license found in the
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// LICENSE file in the root directory of this source tree. An additional grant
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// of patent rights can be found in the PATENTS file in the same directory.
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//
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// Copyright (c) 2011 The LevelDB Authors. All rights reserved.
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// Use of this source code is governed by a BSD-style license that can be
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// found in the LICENSE file. See the AUTHORS file for names of contributors.
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#include <atomic> |
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#include "util/thread_posix.h" |
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#include <unistd.h> |
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#ifdef OS_LINUX |
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#include <sys/syscall.h> |
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#endif |
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namespace rocksdb { |
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void ThreadPool::PthreadCall(const char* label, int result) { |
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if (result != 0) { |
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fprintf(stderr, "pthread %s: %s\n", label, strerror(result)); |
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abort(); |
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} |
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} |
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ThreadPool::ThreadPool() |
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: total_threads_limit_(1), |
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bgthreads_(0), |
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queue_(), |
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queue_len_(0), |
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exit_all_threads_(false), |
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low_io_priority_(false), |
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env_(nullptr) { |
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PthreadCall("mutex_init", pthread_mutex_init(&mu_, nullptr)); |
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PthreadCall("cvar_init", pthread_cond_init(&bgsignal_, nullptr)); |
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} |
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ThreadPool::~ThreadPool() { assert(bgthreads_.size() == 0U); } |
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void ThreadPool::JoinAllThreads() { |
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PthreadCall("lock", pthread_mutex_lock(&mu_)); |
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assert(!exit_all_threads_); |
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exit_all_threads_ = true; |
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PthreadCall("signalall", pthread_cond_broadcast(&bgsignal_)); |
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PthreadCall("unlock", pthread_mutex_unlock(&mu_)); |
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for (const auto tid : bgthreads_) { |
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pthread_join(tid, nullptr); |
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} |
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bgthreads_.clear(); |
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} |
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void ThreadPool::LowerIOPriority() { |
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#ifdef OS_LINUX |
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PthreadCall("lock", pthread_mutex_lock(&mu_)); |
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low_io_priority_ = true; |
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PthreadCall("unlock", pthread_mutex_unlock(&mu_)); |
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#endif |
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} |
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void ThreadPool::BGThread(size_t thread_id) { |
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bool low_io_priority = false; |
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while (true) { |
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// Wait until there is an item that is ready to run
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PthreadCall("lock", pthread_mutex_lock(&mu_)); |
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// Stop waiting if the thread needs to do work or needs to terminate.
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while (!exit_all_threads_ && !IsLastExcessiveThread(thread_id) && |
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(queue_.empty() || IsExcessiveThread(thread_id))) { |
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PthreadCall("wait", pthread_cond_wait(&bgsignal_, &mu_)); |
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} |
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if (exit_all_threads_) { // mechanism to let BG threads exit safely
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PthreadCall("unlock", pthread_mutex_unlock(&mu_)); |
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break; |
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} |
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if (IsLastExcessiveThread(thread_id)) { |
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// Current thread is the last generated one and is excessive.
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// We always terminate excessive thread in the reverse order of
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// generation time.
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auto terminating_thread = bgthreads_.back(); |
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pthread_detach(terminating_thread); |
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bgthreads_.pop_back(); |
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if (HasExcessiveThread()) { |
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// There is still at least more excessive thread to terminate.
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WakeUpAllThreads(); |
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} |
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PthreadCall("unlock", pthread_mutex_unlock(&mu_)); |
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break; |
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} |
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void (*function)(void*) = queue_.front().function; |
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void* arg = queue_.front().arg; |
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queue_.pop_front(); |
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queue_len_.store(static_cast<unsigned int>(queue_.size()), |
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std::memory_order_relaxed); |
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bool decrease_io_priority = (low_io_priority != low_io_priority_); |
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PthreadCall("unlock", pthread_mutex_unlock(&mu_)); |
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#ifdef OS_LINUX |
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if (decrease_io_priority) { |
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#define IOPRIO_CLASS_SHIFT (13) |
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#define IOPRIO_PRIO_VALUE(class, data) (((class) << IOPRIO_CLASS_SHIFT) | data) |
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// Put schedule into IOPRIO_CLASS_IDLE class (lowest)
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// These system calls only have an effect when used in conjunction
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// with an I/O scheduler that supports I/O priorities. As at
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// kernel 2.6.17 the only such scheduler is the Completely
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// Fair Queuing (CFQ) I/O scheduler.
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// To change scheduler:
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// echo cfq > /sys/block/<device_name>/queue/schedule
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// Tunables to consider:
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// /sys/block/<device_name>/queue/slice_idle
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// /sys/block/<device_name>/queue/slice_sync
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syscall(SYS_ioprio_set, 1, // IOPRIO_WHO_PROCESS
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0, // current thread
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IOPRIO_PRIO_VALUE(3, 0)); |
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low_io_priority = true; |
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} |
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#else |
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(void)decrease_io_priority; // avoid 'unused variable' error
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#endif |
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(*function)(arg); |
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} |
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} |
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// Helper struct for passing arguments when creating threads.
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struct BGThreadMetadata { |
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ThreadPool* thread_pool_; |
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size_t thread_id_; // Thread count in the thread.
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explicit BGThreadMetadata(ThreadPool* thread_pool, size_t thread_id) |
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: thread_pool_(thread_pool), thread_id_(thread_id) {} |
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}; |
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static void* BGThreadWrapper(void* arg) { |
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BGThreadMetadata* meta = reinterpret_cast<BGThreadMetadata*>(arg); |
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size_t thread_id = meta->thread_id_; |
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ThreadPool* tp = meta->thread_pool_; |
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#if ROCKSDB_USING_THREAD_STATUS |
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// for thread-status
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ThreadStatusUtil::RegisterThread( |
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tp->GetHostEnv(), (tp->GetThreadPriority() == Env::Priority::HIGH |
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? ThreadStatus::HIGH_PRIORITY |
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: ThreadStatus::LOW_PRIORITY)); |
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#endif |
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delete meta; |
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tp->BGThread(thread_id); |
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#if ROCKSDB_USING_THREAD_STATUS |
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ThreadStatusUtil::UnregisterThread(); |
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#endif |
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return nullptr; |
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} |
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void ThreadPool::WakeUpAllThreads() { |
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PthreadCall("signalall", pthread_cond_broadcast(&bgsignal_)); |
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} |
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void ThreadPool::SetBackgroundThreadsInternal(int num, bool allow_reduce) { |
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PthreadCall("lock", pthread_mutex_lock(&mu_)); |
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if (exit_all_threads_) { |
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PthreadCall("unlock", pthread_mutex_unlock(&mu_)); |
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return; |
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} |
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if (num > total_threads_limit_ || |
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(num < total_threads_limit_ && allow_reduce)) { |
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total_threads_limit_ = std::max(1, num); |
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WakeUpAllThreads(); |
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StartBGThreads(); |
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} |
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PthreadCall("unlock", pthread_mutex_unlock(&mu_)); |
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} |
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void ThreadPool::IncBackgroundThreadsIfNeeded(int num) { |
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SetBackgroundThreadsInternal(num, false); |
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} |
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void ThreadPool::SetBackgroundThreads(int num) { |
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SetBackgroundThreadsInternal(num, true); |
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} |
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void ThreadPool::StartBGThreads() { |
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// Start background thread if necessary
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while ((int)bgthreads_.size() < total_threads_limit_) { |
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pthread_t t; |
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PthreadCall("create thread", |
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pthread_create(&t, nullptr, &BGThreadWrapper, |
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new BGThreadMetadata(this, bgthreads_.size()))); |
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// Set the thread name to aid debugging
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#if defined(_GNU_SOURCE) && defined(__GLIBC_PREREQ) |
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#if __GLIBC_PREREQ(2, 12) |
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char name_buf[16]; |
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snprintf(name_buf, sizeof name_buf, "rocksdb:bg%" ROCKSDB_PRIszt, |
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bgthreads_.size()); |
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name_buf[sizeof name_buf - 1] = '\0'; |
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pthread_setname_np(t, name_buf); |
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#endif |
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#endif |
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bgthreads_.push_back(t); |
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} |
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} |
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void ThreadPool::Schedule(void (*function)(void* arg1), void* arg, void* tag) { |
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PthreadCall("lock", pthread_mutex_lock(&mu_)); |
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if (exit_all_threads_) { |
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PthreadCall("unlock", pthread_mutex_unlock(&mu_)); |
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return; |
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} |
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StartBGThreads(); |
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// Add to priority queue
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queue_.push_back(BGItem()); |
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queue_.back().function = function; |
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queue_.back().arg = arg; |
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queue_.back().tag = tag; |
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queue_len_.store(static_cast<unsigned int>(queue_.size()), |
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std::memory_order_relaxed); |
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if (!HasExcessiveThread()) { |
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// Wake up at least one waiting thread.
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PthreadCall("signal", pthread_cond_signal(&bgsignal_)); |
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} else { |
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// Need to wake up all threads to make sure the one woken
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// up is not the one to terminate.
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WakeUpAllThreads(); |
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} |
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PthreadCall("unlock", pthread_mutex_unlock(&mu_)); |
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} |
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int ThreadPool::UnSchedule(void* arg) { |
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int count = 0; |
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PthreadCall("lock", pthread_mutex_lock(&mu_)); |
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// Remove from priority queue
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BGQueue::iterator it = queue_.begin(); |
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while (it != queue_.end()) { |
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if (arg == (*it).tag) { |
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it = queue_.erase(it); |
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count++; |
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} else { |
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it++; |
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} |
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} |
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queue_len_.store(static_cast<unsigned int>(queue_.size()), |
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std::memory_order_relaxed); |
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PthreadCall("unlock", pthread_mutex_unlock(&mu_)); |
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return count; |
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} |
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} // namespace rocksdb
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@ -0,0 +1,86 @@ |
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// Copyright (c) 2013, Facebook, Inc. All rights reserved.
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// This source code is licensed under the BSD-style license found in the
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// LICENSE file in the root directory of this source tree. An additional grant
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// of patent rights can be found in the PATENTS file in the same directory.
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//
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// Copyright (c) 2011 The LevelDB Authors. All rights reserved.
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// Use of this source code is governed by a BSD-style license that can be
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// found in the LICENSE file. See the AUTHORS file for names of contributors.
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#pragma once |
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#include "rocksdb/env.h" |
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#include "util/thread_status_util.h" |
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namespace rocksdb { |
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class ThreadPool { |
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public: |
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ThreadPool(); |
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~ThreadPool(); |
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void JoinAllThreads(); |
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void LowerIOPriority(); |
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void BGThread(size_t thread_id); |
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void WakeUpAllThreads(); |
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void IncBackgroundThreadsIfNeeded(int num); |
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void SetBackgroundThreads(int num); |
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void StartBGThreads(); |
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void Schedule(void (*function)(void* arg1), void* arg, void* tag); |
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int UnSchedule(void* arg); |
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unsigned int GetQueueLen() const { |
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return queue_len_.load(std::memory_order_relaxed); |
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} |
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void SetHostEnv(Env* env) { env_ = env; } |
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Env* GetHostEnv() { return env_; } |
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// Return true if there is at least one thread needs to terminate.
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bool HasExcessiveThread() { |
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return static_cast<int>(bgthreads_.size()) > total_threads_limit_; |
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} |
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// Return true iff the current thread is the excessive thread to terminate.
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// Always terminate the running thread that is added last, even if there are
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// more than one thread to terminate.
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bool IsLastExcessiveThread(size_t thread_id) { |
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return HasExcessiveThread() && thread_id == bgthreads_.size() - 1; |
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} |
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// Is one of the threads to terminate.
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bool IsExcessiveThread(size_t thread_id) { |
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return static_cast<int>(thread_id) >= total_threads_limit_; |
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} |
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// Return the thread priority.
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// This would allow its member-thread to know its priority.
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Env::Priority GetThreadPriority() { return priority_; } |
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// Set the thread priority.
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void SetThreadPriority(Env::Priority priority) { priority_ = priority; } |
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static void PthreadCall(const char* label, int result); |
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private: |
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// Entry per Schedule() call
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struct BGItem { |
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void* arg; |
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void (*function)(void*); |
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void* tag; |
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}; |
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typedef std::deque<BGItem> BGQueue; |
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pthread_mutex_t mu_; |
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pthread_cond_t bgsignal_; |
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int total_threads_limit_; |
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std::vector<pthread_t> bgthreads_; |
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BGQueue queue_; |
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std::atomic_uint queue_len_; // Queue length. Used for stats reporting
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bool exit_all_threads_; |
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bool low_io_priority_; |
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Env::Priority priority_; |
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Env* env_; |
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void SetBackgroundThreadsInternal(int num, bool allow_reduce); |
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}; |
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} // namespace rocksdb
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