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Unified Diff: base/task_scheduler/scheduler_thread_pool.cc

Issue 1708773002: TaskScheduler [7] SchedulerThreadPool (Closed) Base URL: https://chromium.googlesource.com/chromium/src.git@s_5_worker_thread
Patch Set: self review Created 4 years, 8 months ago
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Index: base/task_scheduler/scheduler_thread_pool.cc
diff --git a/base/task_scheduler/scheduler_thread_pool.cc b/base/task_scheduler/scheduler_thread_pool.cc
new file mode 100644
index 0000000000000000000000000000000000000000..28012d704530bcfd21d0794a6c39d646cd3f7cd8
--- /dev/null
+++ b/base/task_scheduler/scheduler_thread_pool.cc
@@ -0,0 +1,282 @@
+// Copyright 2016 The Chromium Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style license that can be
+// found in the LICENSE file.
+
+#include "base/task_scheduler/scheduler_thread_pool.h"
+
+#include <utility>
+
+#include "base/bind.h"
+#include "base/bind_helpers.h"
+#include "base/lazy_instance.h"
+#include "base/logging.h"
+#include "base/memory/ptr_util.h"
+#include "base/task_scheduler/utils.h"
+#include "base/threading/thread_local.h"
+
+namespace base {
+namespace internal {
+
+namespace {
+
+// SchedulerThreadPool that owns the current thread, if any.
+LazyInstance<ThreadLocalPointer<const SchedulerTaskExecutor>>::Leaky
+ tls_current_thread_pool = LAZY_INSTANCE_INITIALIZER;
+
+// A task runner that runs tasks with the PARALLEL ExecutionMode.
+class SchedulerParallelTaskRunner : public TaskRunner {
+ public:
+ SchedulerParallelTaskRunner(const TaskTraits& traits,
+ TaskTracker* task_tracker,
+ SchedulerTaskExecutor* executor)
+ : traits_(traits), task_tracker_(task_tracker), executor_(executor) {}
+
+ // TaskRunner:
+ bool PostDelayedTask(const tracked_objects::Location& from_here,
+ const Closure& closure,
+ TimeDelta delay) override {
+ // Post the task as part of a one-off single-task Sequence.
+ return PostTaskHelper(from_here, closure, traits_, delay,
+ make_scoped_refptr(new Sequence), executor_,
+ task_tracker_);
+ }
+
+ bool RunsTasksOnCurrentThread() const override {
+ return tls_current_thread_pool.Get().Get() == executor_;
+ }
+
+ private:
+ ~SchedulerParallelTaskRunner() override = default;
+
+ const TaskTraits traits_;
+ TaskTracker* const task_tracker_;
+
+ // TODO(robliao): Use a WeakPtr instead of a raw pointer. A
+ // SchedulerTaskExecutor is never deleted in production, but it's better not
+ // to spread this assumption throughout the scheduler.
gab 2016/04/14 19:34:16 A WeakPtr isn't ever possible here as PostTask is
fdoray 2016/04/14 23:46:58 Done.
+ SchedulerTaskExecutor* const executor_;
+
+ DISALLOW_COPY_AND_ASSIGN(SchedulerParallelTaskRunner);
+};
+
+} // namespace
+
+class SchedulerThreadPool::SchedulerWorkerThreadDelegateImpl
+ : public SchedulerWorkerThread::Delegate {
+ public:
+ SchedulerWorkerThreadDelegateImpl(
+ SchedulerThreadPool* outer,
+ const EnqueueSequenceCallback enqueue_sequence_callback);
+ ~SchedulerWorkerThreadDelegateImpl() override;
+
+ // SchedulerWorkerThread::Delegate:
+ void OnMainEntry() override;
+ scoped_refptr<Sequence> GetWork(
+ SchedulerWorkerThread* worker_thread) override;
+ void EnqueueSequence(scoped_refptr<Sequence> sequence) override;
+
+ private:
+ SchedulerThreadPool* outer_;
+ const EnqueueSequenceCallback enqueue_sequence_callback_;
+
+ DISALLOW_COPY_AND_ASSIGN(SchedulerWorkerThreadDelegateImpl);
+};
+
+SchedulerThreadPool::~SchedulerThreadPool() {
+ // SchedulerThreadPool should never be deleted in production unless its
+ // initialization failed.
+ DCHECK(join_for_testing_returned_.IsSignaled() || worker_threads_.empty());
+}
+
+std::unique_ptr<SchedulerThreadPool> SchedulerThreadPool::CreateThreadPool(
+ ThreadPriority thread_priority,
+ size_t max_threads,
+ const EnqueueSequenceCallback& enqueue_sequence_callback,
+ TaskTracker* task_tracker) {
+ std::unique_ptr<SchedulerThreadPool> thread_pool(
+ new SchedulerThreadPool(enqueue_sequence_callback, task_tracker));
+ if (thread_pool->Initialize(thread_priority, max_threads))
+ return thread_pool;
+ return nullptr;
+}
+
+scoped_refptr<TaskRunner> SchedulerThreadPool::CreateTaskRunnerWithTraits(
+ const TaskTraits& traits,
+ ExecutionMode execution_mode) {
+ switch (execution_mode) {
+ case ExecutionMode::PARALLEL:
+ return make_scoped_refptr(
+ new SchedulerParallelTaskRunner(traits, task_tracker_, this));
+
+ case ExecutionMode::SEQUENCED:
+ case ExecutionMode::SINGLE_THREADED:
+ // TODO(fdoray): Support SEQUENCED and SINGLE_THREADED TaskRunners.
+ NOTREACHED();
+ return nullptr;
+ }
+
+ NOTREACHED();
+ return nullptr;
+}
+
+void SchedulerThreadPool::EnqueueSequence(
+ scoped_refptr<Sequence> sequence,
+ const SequenceSortKey& sequence_sort_key) {
+ shared_priority_queue_.BeginTransaction()->Push(
+ WrapUnique(new PriorityQueue::SequenceAndSortKey(std::move(sequence),
+ sequence_sort_key)));
+
+ // The thread calling this method just ran a Task from |sequence| and will
+ // soon try to get another Sequence from which to run a Task. If the thread
+ // belongs to this pool, it will get that Sequence from
+ // |shared_priority_queue_|. When that's the case, there is no need to wake up
+ // another thread after |sequence| is inserted in |shared_priority_queue_|. If
+ // we did wake up another thread, we would waste resources by having more
+ // threads trying to get a Sequence from |shared_priority_queue_| than the
+ // number of Sequences in it.
+ if (tls_current_thread_pool.Get().Get() != this)
+ WakeUpOneThread();
+}
+
+void SchedulerThreadPool::WaitForAllWorkerThreadsIdleForTesting() {
+ AutoSchedulerLock auto_lock(idle_worker_threads_stack_lock_);
+ while (idle_worker_threads_stack_.size() < worker_threads_.size())
+ idle_worker_threads_stack_cv_for_testing_->Wait();
+}
+
+void SchedulerThreadPool::JoinForTesting() {
+ for (const auto& worker_thread : worker_threads_)
+ worker_thread->JoinForTesting();
+
+ DCHECK(!join_for_testing_returned_.IsSignaled());
+ join_for_testing_returned_.Signal();
+}
+
+void SchedulerThreadPool::PostTaskWithSequence(
+ std::unique_ptr<Task> task,
+ scoped_refptr<Sequence> sequence) {
+ DCHECK(task);
+ DCHECK(sequence);
+
+ // Verify that we are passed |task|'s delayed run time (i.e. |task| is ready
gab 2016/04/14 19:34:16 s/passed/past/ rm "we", e.g.: // Confirm that |t
fdoray 2016/04/14 23:46:58 Done (removed the DCHECK here, kept in in utils.cc
+ // to run).
+ DCHECK_LE(task->delayed_run_time, TimeTicks::Now());
+
+ const bool sequence_was_empty = PostTaskWithSequenceHelper(
+ std::move(task), std::move(sequence), &shared_priority_queue_);
+
+ // No thread has already been woken up to run Tasks from |sequence| if it was
+ // empty before |task| was inserted into it.
+ if (sequence_was_empty)
+ WakeUpOneThread();
+}
+
+SchedulerThreadPool::SchedulerWorkerThreadDelegateImpl::
+ SchedulerWorkerThreadDelegateImpl(
+ SchedulerThreadPool* outer,
+ const EnqueueSequenceCallback enqueue_sequence_callback)
+ : outer_(outer), enqueue_sequence_callback_(enqueue_sequence_callback) {}
+
+SchedulerThreadPool::SchedulerWorkerThreadDelegateImpl::
+ ~SchedulerWorkerThreadDelegateImpl() = default;
+
+void SchedulerThreadPool::SchedulerWorkerThreadDelegateImpl::OnMainEntry() {
+ DCHECK(!tls_current_thread_pool.Get().Get());
+ tls_current_thread_pool.Get().Set(outer_);
+}
+
+scoped_refptr<Sequence>
+SchedulerThreadPool::SchedulerWorkerThreadDelegateImpl::GetWork(
+ SchedulerWorkerThread* worker_thread) {
+ std::unique_ptr<PriorityQueue::Transaction> transaction(
+ outer_->shared_priority_queue_.BeginTransaction());
+ const auto sequence_and_sort_key = transaction->Peek();
+
+ if (sequence_and_sort_key.is_null()) {
+ // |transaction| is kept alive while |worker_thread| is added to
+ // |idle_worker_threads_stack_| to avoid this race:
+ // 1. This thread creates a Transaction, finds |shared_priority_queue_|
+ // empty and ends the Transaction.
+ // 2. Other thread creates a Transaction, inserts a Sequence into
+ // |shared_priority_queue_| and ends the Transaction. This can't happen
+ // if the Transaction of step 1 is still active because because there can
+ // only be one active Transaction per PriorityQueue at a time.
+ // 3. Other thread calls WakeUpOneThread(). No thread is woken up because
+ // |idle_worker_threads_stack_| is empty.
+ // 4. This thread adds itself to |idle_worker_threads_stack_| and goes to
+ // sleep. No thread runs the Sequence inserted in step 2.
+ outer_->AddToIdleWorkerThreadsStack(worker_thread);
+ return nullptr;
+ }
+
+ transaction->Pop();
+ return sequence_and_sort_key.sequence;
+}
+
+void SchedulerThreadPool::SchedulerWorkerThreadDelegateImpl::EnqueueSequence(
+ scoped_refptr<Sequence> sequence) {
+ enqueue_sequence_callback_.Run(std::move(sequence));
+}
+
+SchedulerThreadPool::SchedulerThreadPool(
+ const EnqueueSequenceCallback& enqueue_sequence_callback,
+ TaskTracker* task_tracker)
+ : idle_worker_threads_stack_lock_(shared_priority_queue_.container_lock()),
+ idle_worker_threads_stack_cv_for_testing_(
+ idle_worker_threads_stack_lock_.CreateConditionVariable()),
+ join_for_testing_returned_(true, false),
+ worker_thread_delegate_(
+ new SchedulerWorkerThreadDelegateImpl(this,
+ enqueue_sequence_callback)),
+ task_tracker_(task_tracker) {
+ DCHECK(task_tracker_);
+}
+
+bool SchedulerThreadPool::Initialize(ThreadPriority thread_priority,
+ size_t max_threads) {
+ AutoSchedulerLock auto_lock(idle_worker_threads_stack_lock_);
+
+ DCHECK(worker_threads_.empty());
+
+ for (size_t i = 0; i < max_threads; ++i) {
+ std::unique_ptr<SchedulerWorkerThread> worker_thread =
+ SchedulerWorkerThread::CreateSchedulerWorkerThread(
+ thread_priority, worker_thread_delegate_.get(), task_tracker_);
+ if (!worker_thread)
+ break;
+ idle_worker_threads_stack_.push(worker_thread.get());
+ worker_threads_.push_back(std::move(worker_thread));
+ }
+
+ return !worker_threads_.empty();
+}
+
+void SchedulerThreadPool::WakeUpOneThread() {
+ SchedulerWorkerThread* worker_thread = PopOneIdleWorkerThread();
+ if (worker_thread)
+ worker_thread->WakeUp();
+}
+
+void SchedulerThreadPool::AddToIdleWorkerThreadsStack(
+ SchedulerWorkerThread* worker_thread) {
+ AutoSchedulerLock auto_lock(idle_worker_threads_stack_lock_);
+ idle_worker_threads_stack_.push(worker_thread);
+ DCHECK_LE(idle_worker_threads_stack_.size(), worker_threads_.size());
+
+ if (idle_worker_threads_stack_.size() == worker_threads_.size())
+ idle_worker_threads_stack_cv_for_testing_->Broadcast();
+}
+
+SchedulerWorkerThread* SchedulerThreadPool::PopOneIdleWorkerThread() {
+ AutoSchedulerLock auto_lock(idle_worker_threads_stack_lock_);
+
+ if (idle_worker_threads_stack_.empty())
+ return nullptr;
+
+ auto worker_thread = idle_worker_threads_stack_.top();
+ idle_worker_threads_stack_.pop();
+ return worker_thread;
+}
+
+} // namespace internal
+} // namespace base

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