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// Copyright 2017 The Chromium Authors
// Use of this source code is governed by a BSD-style license that can be
// found in the LICENSE file.
#ifndef COMPONENTS_VIZ_CLIENT_FRAME_EVICTION_MANAGER_H_
#define COMPONENTS_VIZ_CLIENT_FRAME_EVICTION_MANAGER_H_
#include <stddef.h>
#include <list>
#include <map>
#include <memory>
#include <optional>
#include <utility>
#include "base/gtest_prod_util.h"
#include "base/memory/memory_pressure_listener.h"
#include "base/memory/post_delayed_memory_reduction_task.h"
#include "base/memory/raw_ptr.h"
#include "base/memory/singleton.h"
#include "base/task/single_thread_task_runner.h"
#include "base/time/default_tick_clock.h"
#include "base/time/tick_clock.h"
#include "base/timer/timer.h"
#include "base/trace_event/memory_dump_provider.h"
#include "base/trace_event/memory_dump_request_args.h"
#include "components/viz/client/viz_client_export.h"
#if BUILDFLAG(IS_ANDROID)
#include "base/android/pre_freeze_background_memory_trimmer.h"
#endif
namespace viz {
class FrameEvictionManagerClient {
public:
virtual ~FrameEvictionManagerClient() = default;
virtual void EvictCurrentFrame() = 0;
};
// This class is responsible for globally managing which renderers keep their
// compositor frame when offscreen. We actively discard compositor frames for
// offscreen tabs, but keep a minimum amount, as an LRU cache, to make switching
// between a small set of tabs faster. The limit is a soft limit, because
// clients can lock their frame to prevent it from being discarded, e.g. if the
// tab is visible, or while capturing a screenshot.
class VIZ_CLIENT_EXPORT FrameEvictionManager
: public base::trace_event::MemoryDumpProvider {
public:
// Pauses frame eviction within its scope.
class VIZ_CLIENT_EXPORT ScopedPause {
public:
ScopedPause();
ScopedPause(const ScopedPause&) = delete;
ScopedPause& operator=(const ScopedPause&) = delete;
~ScopedPause();
};
static FrameEvictionManager* GetInstance();
FrameEvictionManager(const FrameEvictionManager&) = delete;
FrameEvictionManager& operator=(const FrameEvictionManager&) = delete;
void AddFrame(FrameEvictionManagerClient*, bool locked);
void RemoveFrame(FrameEvictionManagerClient*);
void LockFrame(FrameEvictionManagerClient*);
void UnlockFrame(FrameEvictionManagerClient*);
size_t GetMaxNumberOfSavedFrames() const;
// For testing only
void set_max_number_of_saved_frames(size_t max_number_of_saved_frames) {
max_number_of_saved_frames_ = max_number_of_saved_frames;
}
// React on memory pressure events to adjust the number of cached frames.
// Please make this private when crbug.com/443824 has been fixed.
void OnMemoryPressure(
base::MemoryPressureListener::MemoryPressureLevel memory_pressure_level);
// Purges all unlocked frames, allowing us to reclaim resources.
void PurgeAllUnlockedFrames();
// Chosen arbitrarily, didn't show regressions in metrics during a field trial
// in 2023. Should ideally be higher than a common time to switch between
// tabs. The reasoning is that if a tab isn't switched to in this delay, then
// it's unlikeky to soon be.
static constexpr base::TimeDelta kPeriodicCullingDelay = base::Minutes(5);
private:
friend struct base::DefaultSingletonTraits<FrameEvictionManager>;
FRIEND_TEST_ALL_PREFIXES(FrameEvictionManagerTest, PeriodicCulling);
FrameEvictionManager();
~FrameEvictionManager() override;
void StartFrameCullingTimer();
void CullUnlockedFrames(size_t saved_frame_limit);
#if BUILDFLAG(IS_ANDROID)
void CullOldUnlockedFrames(base::MemoryReductionTaskContext task_type);
#else
void CullOldUnlockedFrames();
#endif
void PurgeMemory(int percentage);
// Pauses/unpauses frame eviction.
void Pause();
void Unpause();
void RegisterUnlockedFrame(FrameEvictionManagerClient* frame);
// Inject mock versions for testing.
void SetOverridesForTesting(
scoped_refptr<base::SingleThreadTaskRunner> task_runner,
const base::TickClock* clock);
bool OnMemoryDump(const base::trace_event::MemoryDumpArgs& args,
base::trace_event::ProcessMemoryDump* pmd) override;
// Listens for system under pressure notifications and adjusts number of
// cached frames accordingly.
std::unique_ptr<base::MemoryPressureListener> memory_pressure_listener_;
std::map<FrameEvictionManagerClient*, size_t> locked_frames_;
// {FrameEvictionManagerClient, Last Unlock() time}, ordered with the most
// recent first.
std::list<std::pair<FrameEvictionManagerClient*, base::TimeTicks>>
unlocked_frames_;
size_t max_number_of_saved_frames_;
// Counter of the outstanding pauses.
int pause_count_ = 0;
// Argument of the last CullUnlockedFrames call while paused.
std::optional<size_t> pending_unlocked_frame_limit_;
base::OneShotDelayedBackgroundTimer idle_frame_culling_timer_;
raw_ptr<const base::TickClock> clock_ = base::DefaultTickClock::GetInstance();
};
} // namespace viz
#endif // COMPONENTS_VIZ_CLIENT_FRAME_EVICTION_MANAGER_H_
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