126 lines
3.3 KiB
C++
126 lines
3.3 KiB
C++
/*
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*
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* Copyright 2015 gRPC authors.
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*
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* Licensed under the Apache License, Version 2.0 (the "License");
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* you may not use this file except in compliance with the License.
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* You may obtain a copy of the License at
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*
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* http://www.apache.org/licenses/LICENSE-2.0
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*
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* Unless required by applicable law or agreed to in writing, software
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* distributed under the License is distributed on an "AS IS" BASIS,
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* WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
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* See the License for the specific language governing permissions and
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* limitations under the License.
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*
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*/
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#include "src/cpp/server/dynamic_thread_pool.h"
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#include <grpc/support/log.h>
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#include <grpcpp/impl/codegen/sync.h>
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#include "src/core/lib/gprpp/thd.h"
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namespace grpc {
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DynamicThreadPool::DynamicThread::DynamicThread(DynamicThreadPool* pool)
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: pool_(pool),
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thd_(
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"grpcpp_dynamic_pool",
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[](void* th) {
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static_cast<DynamicThreadPool::DynamicThread*>(th)->ThreadFunc();
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},
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this) {
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thd_.Start();
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}
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DynamicThreadPool::DynamicThread::~DynamicThread() { thd_.Join(); }
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void DynamicThreadPool::DynamicThread::ThreadFunc() {
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pool_->ThreadFunc();
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// Now that we have killed ourselves, we should reduce the thread count
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grpc_core::MutexLock lock(&pool_->mu_);
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pool_->nthreads_--;
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// Move ourselves to dead list
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pool_->dead_threads_.push_back(this);
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if ((pool_->shutdown_) && (pool_->nthreads_ == 0)) {
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pool_->shutdown_cv_.Signal();
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}
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}
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void DynamicThreadPool::ThreadFunc() {
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for (;;) {
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// Wait until work is available or we are shutting down.
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grpc_core::ReleasableMutexLock lock(&mu_);
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if (!shutdown_ && callbacks_.empty()) {
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// If there are too many threads waiting, then quit this thread
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if (threads_waiting_ >= reserve_threads_) {
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break;
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}
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threads_waiting_++;
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cv_.Wait(&mu_);
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threads_waiting_--;
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}
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// Drain callbacks before considering shutdown to ensure all work
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// gets completed.
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if (!callbacks_.empty()) {
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auto cb = callbacks_.front();
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callbacks_.pop();
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lock.Unlock();
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cb();
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} else if (shutdown_) {
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break;
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}
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}
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}
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DynamicThreadPool::DynamicThreadPool(int reserve_threads)
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: shutdown_(false),
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reserve_threads_(reserve_threads),
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nthreads_(0),
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threads_waiting_(0) {
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for (int i = 0; i < reserve_threads_; i++) {
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grpc_core::MutexLock lock(&mu_);
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nthreads_++;
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new DynamicThread(this);
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}
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}
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void DynamicThreadPool::ReapThreads(std::list<DynamicThread*>* tlist) {
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for (auto t = tlist->begin(); t != tlist->end(); t = tlist->erase(t)) {
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delete *t;
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}
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}
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DynamicThreadPool::~DynamicThreadPool() {
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grpc_core::MutexLock lock(&mu_);
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shutdown_ = true;
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cv_.Broadcast();
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while (nthreads_ != 0) {
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shutdown_cv_.Wait(&mu_);
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}
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ReapThreads(&dead_threads_);
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}
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void DynamicThreadPool::Add(const std::function<void()>& callback) {
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grpc_core::MutexLock lock(&mu_);
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// Add works to the callbacks list
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callbacks_.push(callback);
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// Increase pool size or notify as needed
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if (threads_waiting_ == 0) {
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// Kick off a new thread
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nthreads_++;
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new DynamicThread(this);
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} else {
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cv_.Signal();
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}
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// Also use this chance to harvest dead threads
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if (!dead_threads_.empty()) {
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ReapThreads(&dead_threads_);
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}
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}
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} // namespace grpc
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