// Copyright 2018 The Chromium 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.
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#ifndef BASE_TASK_SCHEDULER_SERVICE_THREAD_H_
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#define BASE_TASK_SCHEDULER_SERVICE_THREAD_H_
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#include "base/base_export.h"
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#include "base/macros.h"
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#include "base/threading/thread.h"
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#include "base/time/time.h"
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#include "base/timer/timer.h"
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namespace base {
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namespace internal {
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class TaskTracker;
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// The TaskScheduler's ServiceThread is a mostly idle thread that is responsible
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// for handling async events (e.g. delayed tasks and async I/O). Its role is to
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// merely forward such events to their destination (hence staying mostly idle
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// and highly responsive).
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// It aliases Thread::Run() to enforce that ServiceThread::Run() be on the stack
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// and make it easier to identify the service thread in stack traces.
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class BASE_EXPORT ServiceThread : public Thread {
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public:
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// Constructs a ServiceThread which will report latency metrics through
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// |task_tracker| if non-null. In that case, this ServiceThread will assume a
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// registered TaskScheduler instance and that |task_tracker| will outlive this
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// ServiceThread.
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explicit ServiceThread(const TaskTracker* task_tracker);
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// Overrides the default interval at which |heartbeat_latency_timer_| fires.
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// Call this with a |heartbeat| of zero to undo the override.
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// Must not be called while the ServiceThread is running.
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static void SetHeartbeatIntervalForTesting(TimeDelta heartbeat);
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private:
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// Thread:
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void Init() override;
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void Run(RunLoop* run_loop) override;
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// Kicks off a single async task which will record a histogram on the latency
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// of a randomly chosen set of TaskTraits.
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void PerformHeartbeatLatencyReport() const;
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const TaskTracker* const task_tracker_;
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// Fires a recurring heartbeat task to record latency histograms which are
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// independent from any execution sequence. This is done on the service thread
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// to avoid all external dependencies (even main thread).
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base::RepeatingTimer heartbeat_latency_timer_;
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DISALLOW_COPY_AND_ASSIGN(ServiceThread);
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};
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} // namespace internal
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} // namespace base
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#endif // BASE_TASK_SCHEDULER_SERVICE_THREAD_H_
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