[scheduler]: Avoid waking up the scheduler to end long idle periods.

components/scheduler/child/idle_helper.cc

 // Copyright 2015 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 "components/scheduler/child/idle_helper.h"
 
 #include "base/trace_event/trace_event.h"
 #include "base/trace_event/trace_event_argument.h"
 #include "components/scheduler/child/scheduler_helper.h"
 
 namespace scheduler {
 
 IdleHelper::IdleHelper(
     SchedulerHelper* helper,
     Delegate* delegate,
     size_t idle_queue_index,
     const char* tracing_category,
     const char* disabled_by_default_tracing_category,
     const char* idle_period_tracing_name,
     base::TimeDelta required_quiescence_duration_before_long_idle_period)
     : helper_(helper),
       delegate_(delegate),
       idle_queue_index_(idle_queue_index),
       idle_period_state_(IdlePeriodState::NOT_IN_IDLE_PERIOD),
       quiescence_monitored_task_queue_mask_(
           helper_->GetQuiescenceMonitoredTaskQueueMask() &
           ~(1ull << idle_queue_index_)),
       required_quiescence_duration_before_long_idle_period_(
           required_quiescence_duration_before_long_idle_period),
+      nestable_events_started_(false),
       tracing_category_(tracing_category),
       disabled_by_default_tracing_category_(
           disabled_by_default_tracing_category),
       idle_period_tracing_name_(idle_period_tracing_name),
       weak_factory_(this) {
   weak_idle_helper_ptr_ = weak_factory_.GetWeakPtr();
-  end_idle_period_closure_.Reset(
-      base::Bind(&IdleHelper::EndIdlePeriod, weak_idle_helper_ptr_));
   enable_next_long_idle_period_closure_.Reset(
       base::Bind(&IdleHelper::EnableLongIdlePeriod, weak_idle_helper_ptr_));
-  enable_next_long_idle_period_after_wakeup_closure_.Reset(base::Bind(
-      &IdleHelper::EnableLongIdlePeriodAfterWakeup, weak_idle_helper_ptr_));
 
   idle_task_runner_ = make_scoped_refptr(new SingleThreadIdleTaskRunner(
       helper_->TaskRunnerForQueue(idle_queue_index_),
-      helper_->ControlAfterWakeUpTaskRunner(),
-      base::Bind(&IdleHelper::CurrentIdleTaskDeadlineCallback,
-                 weak_idle_helper_ptr_),
-      tracing_category));
+      helper_->ControlAfterWakeUpTaskRunner(), this, tracing_category));
 
   helper_->DisableQueue(idle_queue_index_);
   helper_->SetPumpPolicy(idle_queue_index_,
                          TaskQueueManager::PumpPolicy::MANUAL);
+
+  helper_->AddTaskObserver(this);
 }
 
 IdleHelper::~IdleHelper() {
 }
 
 IdleHelper::Delegate::Delegate() {
 }
 
 IdleHelper::Delegate::~Delegate() {
 }
 
 scoped_refptr<SingleThreadIdleTaskRunner> IdleHelper::IdleTaskRunner() {
   helper_->CheckOnValidThread();
   return idle_task_runner_;
 }
 
-void IdleHelper::CurrentIdleTaskDeadlineCallback(
-    base::TimeTicks* deadline_out) const {
-  helper_->CheckOnValidThread();
-  *deadline_out = idle_period_deadline_;
-}
-
 IdleHelper::IdlePeriodState IdleHelper::ComputeNewLongIdlePeriodState(
     const base::TimeTicks now,
     base::TimeDelta* next_long_idle_period_delay_out) {
   helper_->CheckOnValidThread();
 
   if (!delegate_->CanEnterLongIdlePeriod(now,
                                          next_long_idle_period_delay_out)) {
     return IdlePeriodState::NOT_IN_IDLE_PERIOD;
   }
 
@@ skipping 42 matching lines @@
                task_queues_run_since_last_check_bitmap);
 
   // If anything was run on the queues we care about, then we're not quiescent
   // and we should wait.
   return task_queues_run_since_last_check_bitmap != 0;
 }
 
 void IdleHelper::EnableLongIdlePeriod() {
   TRACE_EVENT0(disabled_by_default_tracing_category_, "EnableLongIdlePeriod");
   helper_->CheckOnValidThread();
+  if (helper_->IsShutdown())

[alex clarke (OOO till 29th), 2015/05/27 13:04:17]

Should we have a test for this?

[rmcilroy, 2015/05/27 19:17:05]

Ack - I've not yet added any tests - will do that with the next patch-set.
(just to clarify, this wasn't a bug in the previous implementation - it only
became necessary with the new implementation).

[rmcilroy, 2015/06/01 15:33:22]

Added TestLongIdlePeriodWhenShutdown in latest patch-set.

+    return;
 
   // End any previous idle period.
   EndIdlePeriod();
 
   if (ShouldWaitForQuiescence()) {
     helper_->ControlTaskRunner()->PostDelayedTask(
         FROM_HERE, enable_next_long_idle_period_closure_.callback(),
         required_quiescence_duration_before_long_idle_period_);
     delegate_->IsNotQuiescent();
     return;
   }
 
   base::TimeTicks now(helper_->Now());
   base::TimeDelta next_long_idle_period_delay;
   IdlePeriodState new_idle_period_state =
       ComputeNewLongIdlePeriodState(now, &next_long_idle_period_delay);
   if (IsInIdlePeriod(new_idle_period_state)) {
     StartIdlePeriod(new_idle_period_state, now,
-                    now + next_long_idle_period_delay, false);
-  }
-
-  if (helper_->IsQueueEmpty(idle_queue_index_)) {
-    // If there are no current idle tasks then post the call to initiate the
-    // next idle for execution after wakeup (at which point after-wakeup idle
-    // tasks might be eligible to run or more idle tasks posted).
-    helper_->ControlAfterWakeUpTaskRunner()->PostDelayedTask(
-        FROM_HERE,
-        enable_next_long_idle_period_after_wakeup_closure_.callback(),
-        next_long_idle_period_delay);
+                    now + next_long_idle_period_delay);
   } else {
-    // Otherwise post on the normal control task queue.
+    // Otherwise wait for the next long idle period delay before trying again.
     helper_->ControlTaskRunner()->PostDelayedTask(
         FROM_HERE, enable_next_long_idle_period_closure_.callback(),
         next_long_idle_period_delay);
   }
 }
 
-void IdleHelper::EnableLongIdlePeriodAfterWakeup() {
-  TRACE_EVENT0(disabled_by_default_tracing_category_,
-               "EnableLongIdlePeriodAfterWakeup");
-  helper_->CheckOnValidThread();
-
-  if (IsInIdlePeriod(idle_period_state_)) {
-    // Since we were asleep until now, end the async idle period trace event at
-    // the time when it would have ended were we awake.
-    TRACE_EVENT_ASYNC_END_WITH_TIMESTAMP0(
-        tracing_category_, idle_period_tracing_name_, this,
-        std::min(idle_period_deadline_, helper_->Now()).ToInternalValue());
-    idle_period_state_ = IdlePeriodState::ENDING_LONG_IDLE_PERIOD;
-    EndIdlePeriod();
-  }
-
-  // Post a task to initiate the next long idle period rather than calling it
-  // directly to allow all pending PostIdleTaskAfterWakeup tasks to get enqueued
-  // on the idle task queue before the next idle period starts so they are
-  // eligible to be run during the new idle period.
-  helper_->ControlTaskRunner()->PostTask(
-      FROM_HERE, enable_next_long_idle_period_closure_.callback());
-}
-
 void IdleHelper::StartIdlePeriod(IdlePeriodState new_state,
                                  base::TimeTicks now,
-                                 base::TimeTicks idle_period_deadline,
-                                 bool post_end_idle_period) {
+                                 base::TimeTicks idle_period_deadline) {
   DCHECK_GT(idle_period_deadline, now);
-  TRACE_EVENT_ASYNC_BEGIN0(tracing_category_, idle_period_tracing_name_, this);
   helper_->CheckOnValidThread();
   DCHECK(IsInIdlePeriod(new_state));
+  TRACE_EVENT0(disabled_by_default_tracing_category_, "StartIdlePeriod");
 
   helper_->EnableQueue(idle_queue_index_,
                        PrioritizingTaskQueueSelector::BEST_EFFORT_PRIORITY);
   helper_->PumpQueue(idle_queue_index_);
-  idle_period_state_ = new_state;
 
-  idle_period_deadline_ = idle_period_deadline;
-  if (post_end_idle_period) {
-    helper_->ControlTaskRunner()->PostDelayedTask(
-        FROM_HERE, end_idle_period_closure_.callback(),
-        idle_period_deadline_ - now);
-  }
+  SetIdlePeriodState(new_state, idle_period_deadline, now);
 }
 
 void IdleHelper::EndIdlePeriod() {
   helper_->CheckOnValidThread();
+  TRACE_EVENT0(disabled_by_default_tracing_category_, "EndIdlePeriod");
 
-  end_idle_period_closure_.Cancel();
   enable_next_long_idle_period_closure_.Cancel();
-  enable_next_long_idle_period_after_wakeup_closure_.Cancel();
 
   // If we weren't already within an idle period then early-out.
   if (!IsInIdlePeriod(idle_period_state_))
     return;
 
-  // If we are in the ENDING_LONG_IDLE_PERIOD state we have already logged the
-  // trace event.
-  if (idle_period_state_ != IdlePeriodState::ENDING_LONG_IDLE_PERIOD) {
-    bool is_tracing;
-    TRACE_EVENT_CATEGORY_GROUP_ENABLED(tracing_category_, &is_tracing);
-    if (is_tracing && !idle_period_deadline_.is_null() &&
-        helper_->Now() > idle_period_deadline_) {
-      TRACE_EVENT_ASYNC_STEP_INTO_WITH_TIMESTAMP0(
-          tracing_category_, idle_period_tracing_name_, this, "DeadlineOverrun",
-          idle_period_deadline_.ToInternalValue());
-    }
-    TRACE_EVENT_ASYNC_END0(tracing_category_, idle_period_tracing_name_, this);
-  }
-
   helper_->DisableQueue(idle_queue_index_);
-  idle_period_state_ = IdlePeriodState::NOT_IN_IDLE_PERIOD;
+  SetIdlePeriodState(IdlePeriodState::NOT_IN_IDLE_PERIOD, base::TimeTicks(),
+                     base::TimeTicks());
   idle_period_deadline_ = base::TimeTicks();
 }
 
+void IdleHelper::WillProcessTask(const base::PendingTask& pending_task) {
+}
+
+void IdleHelper::DidProcessTask(const base::PendingTask& pending_task) {
+  helper_->CheckOnValidThread();
+  TRACE_EVENT0(disabled_by_default_tracing_category_, "DidProcessTask");
+  if (IsInIdlePeriod(idle_period_state_) &&
+      idle_period_state_ != IdlePeriodState::IN_LONG_IDLE_PERIOD_PAUSED &&
+      helper_->Now() >= idle_period_deadline_) {
+    // If the idle period deadline has now been reached, either end the idle
+    // period or trigger a new long-idle period.
+    if (IsInLongIdlePeriod(idle_period_state_)) {
+      EnableLongIdlePeriod();
+    } else {
+      DCHECK(IdlePeriodState::IN_SHORT_IDLE_PERIOD == idle_period_state_);
+      EndIdlePeriod();
+    }
+  }
+}
+
+void IdleHelper::UpdateLongIdlePeriodStateAfterIdleTask() {
+  helper_->CheckOnValidThread();
+  DCHECK(IsInLongIdlePeriod(idle_period_state_));
+  TRACE_EVENT0(disabled_by_default_tracing_category_,
+               "UpdateLongIdlePeriodStateAfterIdleTask");
+
+  if (helper_->IsQueueEmpty(idle_queue_index_)) {
+    // If there are no more idle tasks then pause long idle period ticks until a
+    // new idle task is posted.
+    SetIdlePeriodState(IdlePeriodState::IN_LONG_IDLE_PERIOD_PAUSED,
+                       idle_period_deadline_, base::TimeTicks());
+  } else if (helper_->QueueNeedsPumping(idle_queue_index_)) {
+    // If there is still idle work to do then just start the next idle period.
+    base::TimeDelta next_long_idle_period_delay;
+    if (idle_period_state_ ==
+        IdlePeriodState::IN_LONG_IDLE_PERIOD_WITH_MAX_DEADLINE) {
+      // If we are in a max deadline long idle period then start the next
+      // idle period immediately.
+      next_long_idle_period_delay = base::TimeDelta();
+    } else {
+      // Otherwise ensure that we kick the scheduler at the right time to
+      // initiate the next idle period.
+      next_long_idle_period_delay =
+          std::max(base::TimeDelta(), idle_period_deadline_ - helper_->Now());
+    }
+    helper_->ControlTaskRunner()->PostDelayedTask(
+        FROM_HERE, enable_next_long_idle_period_closure_.callback(),
+        next_long_idle_period_delay);
+  }
+}
+
+base::TimeTicks IdleHelper::CurrentIdleTaskDeadline() const {
+  helper_->CheckOnValidThread();
+  return idle_period_deadline_;
+}
+
+void IdleHelper::OnIdleTaskPosted() {
+  helper_->CheckOnValidThread();
+  if (idle_period_state_ == IdlePeriodState::IN_LONG_IDLE_PERIOD_PAUSED) {
+    // Restart long idle period ticks.
+    enable_next_long_idle_period_closure_.Cancel();
+    helper_->ControlTaskRunner()->PostTask(
+        FROM_HERE, enable_next_long_idle_period_closure_.callback());
+  }
+}
+
+base::TimeTicks IdleHelper::WillProcessIdleTask() const {
+  helper_->CheckOnValidThread();
+  DCHECK(IsInIdlePeriod(idle_period_state_));
+  bool is_tracing;
+  TRACE_EVENT_CATEGORY_GROUP_ENABLED(tracing_category_, &is_tracing);
+  if (is_tracing && nestable_events_started_) {
+    last_traced_start_running_idle_task_ =
+        base::TimeTicks::NowFromSystemTraceTime();
+    TRACE_EVENT_NESTABLE_ASYNC_BEGIN_WITH_TIMESTAMP0(
+        tracing_category_, "RunningIdleTask", this,
+        last_traced_start_running_idle_task_.ToInternalValue());
+  }
+  return CurrentIdleTaskDeadline();
+}
+
+void IdleHelper::DidProcessIdleTask() {
+  helper_->CheckOnValidThread();
+  DCHECK(IsInIdlePeriod(idle_period_state_));
+  bool is_tracing;
+  TRACE_EVENT_CATEGORY_GROUP_ENABLED(tracing_category_, &is_tracing);
+  if (is_tracing && nestable_events_started_) {
+    if (!idle_period_deadline_.is_null() &&
+        helper_->Now() > idle_period_deadline_) {
+      TRACE_EVENT_NESTABLE_ASYNC_BEGIN_WITH_TIMESTAMP0(
+          tracing_category_, "DeadlineOverrun", this,
+          std::max(idle_period_deadline_, last_traced_start_running_idle_task_)
+              .ToInternalValue());
+      TRACE_EVENT_NESTABLE_ASYNC_END0(tracing_category_, "DeadlineOverrun",
+                                      this);
+    }
+    TRACE_EVENT_NESTABLE_ASYNC_END0(tracing_category_, "RunningIdleTask", this);
+  }
+
+  if (IsInLongIdlePeriod(idle_period_state_)) {
+    UpdateLongIdlePeriodStateAfterIdleTask();
+  }
+}
+
 // static
 bool IdleHelper::IsInIdlePeriod(IdlePeriodState state) {
   return state != IdlePeriodState::NOT_IN_IDLE_PERIOD;
 }
 
+// static
+bool IdleHelper::IsInLongIdlePeriod(IdlePeriodState state) {
+  return state == IdlePeriodState::IN_LONG_IDLE_PERIOD ||
+         state == IdlePeriodState::IN_LONG_IDLE_PERIOD_WITH_MAX_DEADLINE ||
+         state == IdlePeriodState::IN_LONG_IDLE_PERIOD_PAUSED;
+}
+
+void IdleHelper::SetIdlePeriodState(IdlePeriodState new_state,
+                                    base::TimeTicks new_deadline,
+                                    base::TimeTicks optional_now) {
+  helper_->CheckOnValidThread();
+  if (new_state == idle_period_state_) {
+    DCHECK(new_deadline == idle_period_deadline_);

[Sami, 2015/05/27 12:11:56]

nit: DCHECK_EQ

[rmcilroy, 2015/05/27 19:17:05]

crbug.com/463869 :(

[Sami, 2015/05/29 09:38:06]

I thought we could still use it for TimeTicks?

[rmcilroy, 2015/06/01 15:33:22]

Oops, was looking at the wrong line... Done.

+    return;
+  }
+
+  bool is_tracing;
+  TRACE_EVENT_CATEGORY_GROUP_ENABLED(tracing_category_, &is_tracing);
+  if (is_tracing) {
+    TraceEventIdlePeriodStateChange(new_state, new_deadline, optional_now);
+  }
+
+  idle_period_state_ = new_state;
+  idle_period_deadline_ = new_deadline;
+}
+
 bool IdleHelper::CanExceedIdleDeadlineIfRequired() const {
   TRACE_EVENT0(tracing_category_, "CanExceedIdleDeadlineIfRequired");
   helper_->CheckOnValidThread();
   return idle_period_state_ ==
          IdlePeriodState::IN_LONG_IDLE_PERIOD_WITH_MAX_DEADLINE;
 }
 
 IdleHelper::IdlePeriodState IdleHelper::SchedulerIdlePeriodState() const {
   return idle_period_state_;
 }
 
+void IdleHelper::TraceEventIdlePeriodStateChange(
+    IdlePeriodState new_state,
+    base::TimeTicks new_deadline,
+    base::TimeTicks optional_now) const {
+  TRACE_EVENT2(disabled_by_default_tracing_category_, "SetIdlePeriodState",
+               "old_state",
+               IdleHelper::IdlePeriodStateToString(idle_period_state_),
+               "new_state", IdleHelper::IdlePeriodStateToString(new_state));
+  if (nestable_events_started_) {
+    // End async tracing events for the state we are leaving.
+    if (idle_period_state_ == IdlePeriodState::IN_LONG_IDLE_PERIOD_PAUSED) {
+      TRACE_EVENT_NESTABLE_ASYNC_END0(tracing_category_, "LongIdlePeriodPaused",
+                                      this);
+    }
+    if (IsInLongIdlePeriod(idle_period_state_) &&
+        !IsInLongIdlePeriod(new_state)) {
+      TRACE_EVENT_NESTABLE_ASYNC_END0(tracing_category_, "LongIdlePeriod",
+                                      this);
+    }
+    if (idle_period_state_ == IdlePeriodState::IN_SHORT_IDLE_PERIOD) {
+      TRACE_EVENT_NESTABLE_ASYNC_END0(tracing_category_, "ShortIdlePeriod",
+                                      this);
+    }
+    if (IsInIdlePeriod(idle_period_state_) && !IsInIdlePeriod(new_state)) {
+      TRACE_EVENT_NESTABLE_ASYNC_END0(tracing_category_,
+                                      idle_period_tracing_name_, this);
+      nestable_events_started_ = false;
+    }
+  }
+
+  // Start async tracing events for the state we are entering.
+  if (IsInIdlePeriod(new_state) && !IsInIdlePeriod(idle_period_state_)) {
+    if (optional_now.is_null())
+      optional_now = helper_->Now();
+    nestable_events_started_ = true;
+    TRACE_EVENT_NESTABLE_ASYNC_BEGIN1(
+        tracing_category_, idle_period_tracing_name_, this,
+        "idle_period_length_ms",
+        (new_deadline - optional_now).ToInternalValue());
+  }
+  if (new_state == IdlePeriodState::IN_SHORT_IDLE_PERIOD) {
+    TRACE_EVENT_NESTABLE_ASYNC_BEGIN0(tracing_category_, "ShortIdlePeriod",
+                                      this);
+  }
+  if (IsInLongIdlePeriod(new_state) &&
+      !IsInLongIdlePeriod(idle_period_state_)) {
+    TRACE_EVENT_NESTABLE_ASYNC_BEGIN0(tracing_category_, "LongIdlePeriod",
+                                      this);
+  }
+  if (new_state == IdlePeriodState::IN_LONG_IDLE_PERIOD_PAUSED) {
+    TRACE_EVENT_NESTABLE_ASYNC_BEGIN0(tracing_category_, "LongIdlePeriodPaused",
+                                      this);
+  }
+}
+
 // static
 const char* IdleHelper::IdlePeriodStateToString(
     IdlePeriodState idle_period_state) {
   switch (idle_period_state) {
     case IdlePeriodState::NOT_IN_IDLE_PERIOD:
       return "not_in_idle_period";
     case IdlePeriodState::IN_SHORT_IDLE_PERIOD:
       return "in_short_idle_period";
     case IdlePeriodState::IN_LONG_IDLE_PERIOD:
       return "in_long_idle_period";
     case IdlePeriodState::IN_LONG_IDLE_PERIOD_WITH_MAX_DEADLINE:
       return "in_long_idle_period_with_max_deadline";
-    case IdlePeriodState::ENDING_LONG_IDLE_PERIOD:
-      return "ending_long_idle_period";
+    case IdlePeriodState::IN_LONG_IDLE_PERIOD_PAUSED:
+      return "in_long_idle_period_paused";
     default:
       NOTREACHED();
       return nullptr;
   }
 }
 
 }  // namespace scheduler