Use the scheduling mechanism provided by the platform

Source/platform/scheduler/Scheduler.cpp

 // Copyright 2014 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 "config.h"
 #include "platform/scheduler/Scheduler.h"
 
-#include "platform/PlatformThreadData.h"
-#include "platform/RuntimeEnabledFeatures.h"
-#include "platform/Task.h"
-#include "platform/ThreadTimers.h"
-#include "platform/TraceEvent.h"
+#include "platform/TraceLocation.h"
 #include "public/platform/Platform.h"
-#include "wtf/MainThread.h"
+#include "public/platform/WebScheduler.h"
 
 namespace blink {
 
-namespace {
-
-// The time we should stay in CompositorPriority mode for, after a touch event.
-double kLowSchedulerPolicyAfterTouchTimeSeconds = 0.1;
-
-} // namespace
-
-// Typically only created from compositor or render threads.
-// Note if the scheduler gets shutdown, this may be run after.
-class Scheduler::MainThreadPendingHighPriorityTaskRunner : public WebThread::Task {
+class IdleTaskRunner : public WebScheduler::IdleTask {
 public:
-    MainThreadPendingHighPriorityTaskRunner(
-        const Scheduler::Task& task, const TraceLocation& location, const char* traceName)
-        : m_task(internal::TracedStandardTask::Create(task, location, traceName))
+    explicit IdleTaskRunner(const Scheduler::IdleTask& task)
+        : m_task(task)
     {
-        ASSERT(Scheduler::shared());
     }
 
-    // WebThread::Task implementation.
-    virtual void run() override
+    virtual ~IdleTaskRunner()
     {
-        m_task->run();
-        if (Scheduler* scheduler = Scheduler::shared()) {
-            scheduler->updatePolicy();
-            scheduler->didRunHighPriorityTask();
-        }
     }
 
+    // WebScheduler::IdleTask implementation.
+    void run(double deadlineSeconds) override
+    {
+        m_task(deadlineSeconds);
+    }
 private:
-    OwnPtr<internal::TracedStandardTask> m_task;
+    Scheduler::IdleTask m_task;
 };
 
-// Can be created from any thread.
-// Note if the scheduler gets shutdown, this may be run after.
-class Scheduler::MainThreadPendingTaskRunner : public WebThread::Task {
-public:
-    MainThreadPendingTaskRunner(
-        const Scheduler::Task& task, const TraceLocation& location, const char* traceName)
-        : m_task(internal::TracedStandardTask::Create(task, location, traceName))
-    {
-        ASSERT(Scheduler::shared());
-    }
-
-    // WebThread::Task implementation.
-    virtual void run() override
-    {
-        m_task->run();
-        if (Scheduler* scheduler = Scheduler::shared()) {
-            scheduler->updatePolicy();
-        }
-    }
-
-private:
-    OwnPtr<internal::TracedStandardTask> m_task;
-};
-
-
-// Can be created from any thread.
-// Note if the scheduler gets shutdown, this may be run after.
-class Scheduler::MainThreadPendingIdleTaskRunner : public WebThread::Task {
-public:
-    MainThreadPendingIdleTaskRunner()
-    {
-        ASSERT(Scheduler::shared());
-    }
-
-    // WebThread::Task implementation.
-    virtual void run() override
-    {
-        if (Scheduler* scheduler = Scheduler::shared()) {
-            scheduler->maybeRunPendingIdleTask();
-            // If possible, run the next idle task by reposting on the main thread.
-            scheduler->maybePostMainThreadPendingIdleTask();
-        }
-    }
-
-};
-
-
 Scheduler* Scheduler::s_sharedScheduler = nullptr;
 
-void Scheduler::initializeOnMainThread()
-{
-    s_sharedScheduler = new Scheduler();
-}
-
 void Scheduler::shutdown()
 {
     delete s_sharedScheduler;
     s_sharedScheduler = nullptr;
 }
 
 Scheduler* Scheduler::shared()
 {
+    if (!s_sharedScheduler)
+        s_sharedScheduler = new Scheduler(Platform::current()->scheduler());
     return s_sharedScheduler;
 }
 
-Scheduler::Scheduler()
-    : m_sharedTimerFunction(nullptr)
-    , m_mainThread(blink::Platform::current()->currentThread())
-    , m_estimatedNextBeginFrameSeconds(0)
-    , m_highPriorityTaskCount(0)
-    , m_highPriorityTaskRunnerPosted(false)
-    , m_compositorPriorityPolicyEndTimeSeconds(0)
-    , m_schedulerPolicy(Normal)
+Scheduler::Scheduler(WebScheduler* webScheduler)
+    : m_webScheduler(webScheduler)
 {
 }
 
 Scheduler::~Scheduler()
 {
-}
-
-void Scheduler::willBeginFrame(double estimatedNextBeginFrameSeconds)
-{
-    ASSERT(isMainThread());
-    m_currentFrameCommitted = false;
-    m_estimatedNextBeginFrameSeconds = estimatedNextBeginFrameSeconds;
-    // TODO: Schedule a deferred task here to run idle work if didCommitFrameToCompositor never gets called.
-}
-
-void Scheduler::didCommitFrameToCompositor()
-{
-    ASSERT(isMainThread());
-    m_currentFrameCommitted = true;
-    flushIncomingIdleTasks();
-    maybePostMainThreadPendingIdleTask();
-}
-
-void Scheduler::postHighPriorityTaskInternal(const TraceLocation& location, const Task& task, const char* traceName)
-{
-    m_mainThread->postTask(new MainThreadPendingHighPriorityTaskRunner(task, location, traceName));
-    atomicIncrement(&m_highPriorityTaskCount);
-    TRACE_COUNTER1(TRACE_DISABLED_BY_DEFAULT("blink.scheduler"), "PendingHighPriorityTasks", m_highPriorityTaskCount);
-}
-
-void Scheduler::didRunHighPriorityTask()
-{
-    atomicDecrement(&m_highPriorityTaskCount);
-    TRACE_COUNTER1(TRACE_DISABLED_BY_DEFAULT("blink.scheduler"), "PendingHighPriorityTasks", m_highPriorityTaskCount);
-}
-
-void Scheduler::postIdleTaskInternal(const TraceLocation& location, const IdleTask& idleTask, const char* traceName)
-{
-    Locker<Mutex> lock(m_incomingIdleTasksMutex);
-    m_incomingIdleTasks.append(internal::TracedIdleTask::Create(idleTask, location, traceName));
-}
-
-void Scheduler::postTask(const TraceLocation& location, const Task& task)
-{
-    m_mainThread->postTask(new MainThreadPendingTaskRunner(task, location, "Scheduler::MainThreadTask"));
-}
-
-void Scheduler::postInputTask(const TraceLocation& location, const Task& task)
-{
-    postHighPriorityTaskInternal(location, task, "Scheduler::InputTask");
-}
-
-void Scheduler::didReceiveInputEvent()
-{
-    // FIXME: We probably want an explicit Disabled policy rather than disabling CompositorPriority.
-    if (RuntimeEnabledFeatures::blinkSchedulerEnabled())
-        enterSchedulerPolicy(CompositorPriority);
-}
-
-void Scheduler::postCompositorTask(const TraceLocation& location, const Task& task)
-{
-    postHighPriorityTaskInternal(location, task, "Scheduler::CompositorTask");
-}
-
-void Scheduler::postIpcTask(const TraceLocation& location, const Task& task)
-{
-    // FIXME: we want IPCs to be high priority, but we can't currently do that because some of them can take a very long
-    // time to process. These need refactoring but we need to add some infrastructure to identify them.
-    m_mainThread->postTask(new MainThreadPendingTaskRunner(task, location, "Scheduler::IpcTask"));
+    if (m_webScheduler)
+        m_webScheduler->shutdown();
 }
 
 void Scheduler::postIdleTask(const TraceLocation& location, const IdleTask& idleTask)
 {
-    postIdleTaskInternal(location, idleTask, "Scheduler::IdleTask");
-}
-
-bool Scheduler::maybePostMainThreadPendingIdleTask()
-{
-    ASSERT(isMainThread());
-    TRACE_EVENT0("blink", "Scheduler::maybePostMainThreadPendingIdleTask");
-    if (canRunIdleTask()) {
-        if (!m_pendingIdleTasks.isEmpty()) {
-            m_mainThread->postTask(new MainThreadPendingIdleTaskRunner());
-            return true;
-        }
-    }
-    return false;
-}
-
-void Scheduler::tickSharedTimer()
-{
-    TRACE_EVENT0("blink", "Scheduler::tickSharedTimer");
-    m_sharedTimerFunction();
-}
-
-void Scheduler::updatePolicy()
-{
-    ASSERT(isMainThread());
-    Locker<Mutex> lock(m_policyStateMutex);
-
-    // Go back to the normal scheduler policy if enough time has elapsed.
-    if (schedulerPolicy() == CompositorPriority && Platform::current()->monotonicallyIncreasingTime() > m_compositorPriorityPolicyEndTimeSeconds)
-        enterSchedulerPolicyLocked(Normal);
-}
-
-void Scheduler::sharedTimerAdapter()
-{
-    shared()->tickSharedTimer();
-}
-
-void Scheduler::setSharedTimerFiredFunction(void (*function)())
-{
-    m_sharedTimerFunction = function;
-    blink::Platform::current()->setSharedTimerFiredFunction(function ? &Scheduler::sharedTimerAdapter : nullptr);
-}
-
-void Scheduler::setSharedTimerFireInterval(double interval)
-{
-    blink::Platform::current()->setSharedTimerFireInterval(interval);
-}
-
-void Scheduler::stopSharedTimer()
-{
-    blink::Platform::current()->stopSharedTimer();
+    if (m_webScheduler)
+        m_webScheduler->postIdleTask(location.toWebTraceLocation(), new IdleTaskRunner(idleTask));
 }
 
 bool Scheduler::shouldYieldForHighPriorityWork() const
 {
-    // It's only worthwhile yielding in CompositorPriority mode.
-    if (schedulerPolicy() != CompositorPriority)
-        return false;
-
-    // This method is expected to be run on the main thread, but the high priority tasks will be posted by
-    // other threads. We could use locks here, but this function is (sometimes) called a lot by
-    // ThreadTimers::sharedTimerFiredInternal so we decided to use atomics + barrier loads here which
-    // should be cheaper.
-    // NOTE it's possible the barrier read is overkill here, since delayed yielding isn't a big deal.
-    return acquireLoad(&m_highPriorityTaskCount) != 0;
-}
-
-bool Scheduler::maybeRunPendingIdleTask()
-{
-    ASSERT(isMainThread());
-    if (!canRunIdleTask() || m_pendingIdleTasks.isEmpty())
-        return false;
-
-    m_pendingIdleTasks.takeFirst()->run();
-    return true;
-}
-
-void Scheduler::flushIncomingIdleTasks()
-{
-    ASSERT(isMainThread());
-    Locker<Mutex> lock(m_incomingIdleTasksMutex);
-    while (!m_incomingIdleTasks.isEmpty())
-        m_pendingIdleTasks.append(m_incomingIdleTasks.takeFirst());
-}
-
-double Scheduler::currentFrameDeadlineForIdleTasks() const
-{
-    ASSERT(isMainThread());
-    // TODO: Make idle time more fine-grain chunks when in Compositor priority.
-    return m_estimatedNextBeginFrameSeconds;
-}
-
-bool Scheduler::canRunIdleTask() const
-{
-    ASSERT(isMainThread());
-    return m_currentFrameCommitted
-        && !shouldYieldForHighPriorityWork()
-        && (m_estimatedNextBeginFrameSeconds > Platform::current()->monotonicallyIncreasingTime());
-}
-
-Scheduler::SchedulerPolicy Scheduler::schedulerPolicy() const
-{
-    ASSERT(isMainThread());
-    // It's important not to miss the transition from normal to low latency mode, otherwise we're likely to
-    // delay the processing of input tasks. Since that transition is triggered by a different thread, we
-    // need either a lock or a memory barrier, and the memory barrier is probably cheaper.
-    return static_cast<SchedulerPolicy>(acquireLoad(&m_schedulerPolicy));
-}
-
-void Scheduler::enterSchedulerPolicy(SchedulerPolicy schedulerPolicy)
-{
-    Locker<Mutex> lock(m_policyStateMutex);
-    enterSchedulerPolicyLocked(schedulerPolicy);
-}
-
-void Scheduler::enterSchedulerPolicyLocked(SchedulerPolicy schedulerPolicy)
-{
-    ASSERT(m_policyStateMutex.locked());
-    if (schedulerPolicy == CompositorPriority)
-        m_compositorPriorityPolicyEndTimeSeconds = Platform::current()->monotonicallyIncreasingTime() + kLowSchedulerPolicyAfterTouchTimeSeconds;
-
-    releaseStore(&m_schedulerPolicy, schedulerPolicy);
-    TRACE_COUNTER1(TRACE_DISABLED_BY_DEFAULT("blink.scheduler"), "SchedulerPolicy", schedulerPolicy);
+    if (m_webScheduler)
+        return m_webScheduler->shouldYieldForHighPriorityWork();
+    return false;
 }
 
 } // namespace blink