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// 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.
#ifndef THIRD_PARTY_BLINK_RENDERER_PLATFORM_SCHEDULER_MAIN_THREAD_AUTO_ADVANCING_VIRTUAL_TIME_DOMAIN_H_
#define THIRD_PARTY_BLINK_RENDERER_PLATFORM_SCHEDULER_MAIN_THREAD_AUTO_ADVANCING_VIRTUAL_TIME_DOMAIN_H_
#include "base/macros.h"
#include "base/task/sequence_manager/time_domain.h"
#include "base/task/task_observer.h"
#include "base/time/time_override.h"
#include "third_party/blink/renderer/platform/platform_export.h"
namespace blink {
namespace scheduler {
class SchedulerHelper;
// A time domain that runs tasks sequentially in time order but doesn't sleep
// between delayed tasks.
//
// KEY: A-E are delayed tasks
// | A B C D E (Execution with RealTimeDomain)
// |-----------------------------> time
//
// |ABCDE (Execution with AutoAdvancingVirtualTimeDomain)
// |-----------------------------> time
class PLATFORM_EXPORT AutoAdvancingVirtualTimeDomain
: public base::sequence_manager::TimeDomain,
public base::TaskObserver {
public:
enum class BaseTimeOverridePolicy { OVERRIDE, DO_NOT_OVERRIDE };
AutoAdvancingVirtualTimeDomain(base::Time initial_time,
base::TimeTicks initial_time_ticks,
SchedulerHelper* helper,
BaseTimeOverridePolicy policy);
~AutoAdvancingVirtualTimeDomain() override;
// Controls whether or not virtual time is allowed to advance, when the
// SequenceManager runs out of immediate work to do.
void SetCanAdvanceVirtualTime(bool can_advance_virtual_time);
// If non-null, virtual time may not advance past |virtual_time_fence|.
void SetVirtualTimeFence(base::TimeTicks virtual_time_fence);
// The maximum number amount of delayed task starvation we will allow.
// NB a value of 0 allows infinite starvation. A reasonable value for this in
// practice is around 1000 tasks, which should only affect rendering of the
// heaviest pages.
void SetMaxVirtualTimeTaskStarvationCount(int max_task_starvation_count);
// Updates to min(NextDelayedTaskTime, |new_virtual_time|) if thats ahead of
// the current virtual time. Returns true if time was advanced.
bool MaybeAdvanceVirtualTime(base::TimeTicks new_virtual_time);
// base::PendingTask implementation:
void WillProcessTask(const base::PendingTask& pending_task,
bool was_blocked_or_low_priority) override;
void DidProcessTask(const base::PendingTask& pending_task) override;
int task_starvation_count() const { return task_starvation_count_; }
// TimeDomain implementation:
base::sequence_manager::LazyNow CreateLazyNow() const override;
base::TimeTicks Now() const override;
absl::optional<base::TimeDelta> DelayTillNextTask(
base::sequence_manager::LazyNow* lazy_now) override;
bool MaybeFastForwardToNextTask(bool quit_when_idle_requested) override;
protected:
const char* GetName() const override;
void SetNextDelayedDoWork(base::sequence_manager::LazyNow* lazy_now,
base::TimeTicks run_time) override;
private:
// Can be called on any thread.
base::Time Date() const;
// For base time overriding.
static base::TimeTicks GetVirtualTimeTicks();
static base::Time GetVirtualTime();
static AutoAdvancingVirtualTimeDomain* g_time_domain_;
// The number of tasks that have been run since the last time VirtualTime
// advanced. Used to detect excessive starvation of delayed tasks.
int task_starvation_count_;
// The maximum number amount of delayed task starvation we will allow.
// NB a value of 0 allows infinite starvation.
int max_task_starvation_count_;
bool can_advance_virtual_time_;
SchedulerHelper* helper_; // NOT OWNED
// VirtualTime is usually doled out in 100ms intervals using fences and this
// variable let us honor a request to MaybeAdvanceVirtualTime that straddles
// one of these boundaries.
base::TimeTicks requested_next_virtual_time_;
// Upper limit on how far virtual time is allowed to advance.
base::TimeTicks virtual_time_fence_;
mutable base::Lock now_ticks_lock_;
base::TimeTicks now_ticks_;
const base::TimeTicks initial_time_ticks_;
const base::Time initial_time_;
base::Time previous_time_;
std::unique_ptr<base::subtle::ScopedTimeClockOverrides> time_overrides_;
DISALLOW_COPY_AND_ASSIGN(AutoAdvancingVirtualTimeDomain);
};
} // namespace scheduler
} // namespace blink
#endif // THIRD_PARTY_BLINK_RENDERER_PLATFORM_SCHEDULER_MAIN_THREAD_AUTO_ADVANCING_VIRTUAL_TIME_DOMAIN_H_
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