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Diffstat (limited to 'src/cpp/thread_manager/thread_manager.cc')
-rw-r--r-- | src/cpp/thread_manager/thread_manager.cc | 181 |
1 files changed, 181 insertions, 0 deletions
diff --git a/src/cpp/thread_manager/thread_manager.cc b/src/cpp/thread_manager/thread_manager.cc new file mode 100644 index 0000000000..caae4c457d --- /dev/null +++ b/src/cpp/thread_manager/thread_manager.cc @@ -0,0 +1,181 @@ +/* + * + * Copyright 2016, Google Inc. + * All rights reserved. + * + * Redistribution and use in source and binary forms, with or without + * modification, are permitted provided that the following conditions are + * met: + * + * * Redistributions of source code must retain the above copyright + * notice, this list of conditions and the following disclaimer. + * * Redistributions in binary form must reproduce the above + * copyright notice, this list of conditions and the following disclaimer + * in the documentation and/or other materials provided with the + * distribution. + * * Neither the name of Google Inc. nor the names of its + * contributors may be used to endorse or promote products derived from + * this software without specific prior written permission. + * + * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS + * "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT + * LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR + * A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT + * OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, + * SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT + * LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, + * DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY + * THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT + * (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE + * OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE. + * + */ + +#include <grpc++/impl/sync.h> +#include <grpc++/impl/thd.h> +#include <grpc/support/log.h> +#include <climits> + +#include "src/cpp/thread_manager/thread_manager.h" + +namespace grpc { + +ThreadManager::WorkerThread::WorkerThread(ThreadManager* thd_mgr) + : thd_mgr_(thd_mgr), thd_(&ThreadManager::WorkerThread::Run, this) {} + +void ThreadManager::WorkerThread::Run() { + thd_mgr_->MainWorkLoop(); + thd_mgr_->MarkAsCompleted(this); +} + +ThreadManager::WorkerThread::~WorkerThread() { thd_.join(); } + +ThreadManager::ThreadManager(int min_pollers, int max_pollers) + : shutdown_(false), + num_pollers_(0), + min_pollers_(min_pollers), + max_pollers_(max_pollers == -1 ? INT_MAX : max_pollers), + num_threads_(0) {} + +ThreadManager::~ThreadManager() { + { + std::unique_lock<grpc::mutex> lock(mu_); + GPR_ASSERT(num_threads_ == 0); + } + + CleanupCompletedThreads(); +} + +void ThreadManager::Wait() { + std::unique_lock<grpc::mutex> lock(mu_); + while (num_threads_ != 0) { + shutdown_cv_.wait(lock); + } +} + +void ThreadManager::Shutdown() { + std::unique_lock<grpc::mutex> lock(mu_); + shutdown_ = true; +} + +bool ThreadManager::IsShutdown() { + std::unique_lock<grpc::mutex> lock(mu_); + return shutdown_; +} + +void ThreadManager::MarkAsCompleted(WorkerThread* thd) { + { + std::unique_lock<grpc::mutex> list_lock(list_mu_); + completed_threads_.push_back(thd); + } + + grpc::unique_lock<grpc::mutex> lock(mu_); + num_threads_--; + if (num_threads_ == 0) { + shutdown_cv_.notify_one(); + } +} + +void ThreadManager::CleanupCompletedThreads() { + std::unique_lock<grpc::mutex> lock(list_mu_); + for (auto thd = completed_threads_.begin(); thd != completed_threads_.end(); + thd = completed_threads_.erase(thd)) { + delete *thd; + } +} + +void ThreadManager::Initialize() { + for (int i = 0; i < min_pollers_; i++) { + MaybeCreatePoller(); + } +} + +// If the number of pollers (i.e threads currently blocked in PollForWork()) is +// less than max threshold (i.e max_pollers_) and the total number of threads is +// below the maximum threshold, we can let the current thread continue as poller +bool ThreadManager::MaybeContinueAsPoller() { + std::unique_lock<grpc::mutex> lock(mu_); + if (shutdown_ || num_pollers_ > max_pollers_) { + return false; + } + + num_pollers_++; + return true; +} + +// Create a new poller if the current number of pollers i.e num_pollers_ (i.e +// threads currently blocked in PollForWork()) is below the threshold (i.e +// min_pollers_) and the total number of threads is below the maximum threshold +void ThreadManager::MaybeCreatePoller() { + grpc::unique_lock<grpc::mutex> lock(mu_); + if (!shutdown_ && num_pollers_ < min_pollers_) { + num_pollers_++; + num_threads_++; + + // Create a new thread (which ends up calling the MainWorkLoop() function + new WorkerThread(this); + } +} + +void ThreadManager::MainWorkLoop() { + void* tag; + bool ok; + + /* + 1. Poll for work (i.e PollForWork()) + 2. After returning from PollForWork, reduce the number of pollers by 1. If + PollForWork() returned a TIMEOUT, then it may indicate that we have more + polling threads than needed. Check if the number of pollers is greater + than min_pollers and if so, terminate the thread. + 3. Since we are short of one poller now, see if a new poller has to be + created (i.e see MaybeCreatePoller() for more details) + 4. Do the actual work (DoWork()) + 5. After doing the work, see it this thread can resume polling work (i.e + see MaybeContinueAsPoller() for more details) */ + do { + WorkStatus work_status = PollForWork(&tag, &ok); + + { + grpc::unique_lock<grpc::mutex> lock(mu_); + num_pollers_--; + + if (work_status == TIMEOUT && num_pollers_ > min_pollers_) { + break; + } + } + + // Note that MaybeCreatePoller does check for shutdown and creates a new + // thread only if ThreadManager is not shutdown + if (work_status == WORK_FOUND) { + MaybeCreatePoller(); + DoWork(tag, ok); + } + } while (MaybeContinueAsPoller()); + + CleanupCompletedThreads(); + + // If we are here, either ThreadManager is shutting down or it already has + // enough threads. +} + +} // namespace grpc |