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// Copyright 2019 The Chromium Authors
// Use of this source code is governed by a BSD-style license that can be
// found in the LICENSE file.
#include "components/memory_pressure/memory_pressure_voter.h"
#include <numeric>
#include <optional>
#include "base/memory/raw_ptr.h"
#include "base/trace_event/trace_event.h"
namespace memory_pressure {
class MemoryPressureVoterImpl : public MemoryPressureVoter {
public:
explicit MemoryPressureVoterImpl(MemoryPressureVoteAggregator* aggregator)
: aggregator_(aggregator) {}
~MemoryPressureVoterImpl() override {
// Remove this voter's vote.
if (vote_) {
aggregator_->OnVote(vote_, std::nullopt);
}
}
MemoryPressureVoterImpl(MemoryPressureVoterImpl&&) = delete;
MemoryPressureVoterImpl& operator=(MemoryPressureVoterImpl&&) = delete;
void SetVote(base::MemoryPressureListener::MemoryPressureLevel level,
bool notify_listeners) override {
DCHECK_CALLED_ON_VALID_SEQUENCE(sequence_checker_);
auto old_vote = vote_;
vote_ = level;
aggregator_->OnVote(old_vote, vote_);
if (notify_listeners) {
aggregator_->NotifyListeners();
}
}
private:
// This is the aggregator to which this voter's votes will be cast.
const raw_ptr<MemoryPressureVoteAggregator> aggregator_;
// optional<> is used here as the vote will be null until the voter's
// first vote calculation.
std::optional<base::MemoryPressureListener::MemoryPressureLevel> vote_;
SEQUENCE_CHECKER(sequence_checker_);
};
MemoryPressureVoteAggregator::MemoryPressureVoteAggregator(Delegate* delegate)
: delegate_(delegate) {}
MemoryPressureVoteAggregator::~MemoryPressureVoteAggregator() {
DCHECK_EQ(std::accumulate(votes_.begin(), votes_.end(), 0), 0);
}
std::unique_ptr<MemoryPressureVoter>
MemoryPressureVoteAggregator::CreateVoter() {
return std::make_unique<MemoryPressureVoterImpl>(this);
}
void MemoryPressureVoteAggregator::OnVoteForTesting(
std::optional<MemoryPressureLevel> old_vote,
std::optional<MemoryPressureLevel> new_vote) {
OnVote(old_vote, new_vote);
}
void MemoryPressureVoteAggregator::NotifyListenersForTesting() {
NotifyListeners();
}
base::MemoryPressureListener::MemoryPressureLevel
MemoryPressureVoteAggregator::EvaluateVotesForTesting() {
return EvaluateVotes();
}
void MemoryPressureVoteAggregator::OnVote(
std::optional<MemoryPressureLevel> old_vote,
std::optional<MemoryPressureLevel> new_vote) {
DCHECK_CALLED_ON_VALID_SEQUENCE(sequence_checker_);
DCHECK(old_vote || new_vote);
if (old_vote) {
DCHECK_LT(0u, votes_[old_vote.value()]);
votes_[old_vote.value()]--;
}
if (new_vote) {
votes_[new_vote.value()]++;
}
auto old_pressure_level = current_pressure_level_;
// If the pressure level is not None then an asynchronous event will have been
// started below, it needs to be ended.
// Note that we record this event every time we receive a new vote to ensure
// that the begin event doesn't get dropped during long pressure sessions.
if (old_pressure_level ==
MemoryPressureLevel::MEMORY_PRESSURE_LEVEL_CRITICAL) {
TRACE_EVENT_NESTABLE_ASYNC_END0("base", "MemoryPressure::CriticalPressure",
this);
} else if (old_pressure_level ==
MemoryPressureLevel::MEMORY_PRESSURE_LEVEL_MODERATE) {
TRACE_EVENT_NESTABLE_ASYNC_END0("base", "MemoryPressure::ModeratePressure",
this);
}
current_pressure_level_ = EvaluateVotes();
// Start an asynchronous tracing event to record this pressure session.
if (current_pressure_level_ ==
MemoryPressureLevel::MEMORY_PRESSURE_LEVEL_CRITICAL) {
TRACE_EVENT_NESTABLE_ASYNC_BEGIN0("base",
"MemoryPressure::CriticalPressure", this);
} else if (current_pressure_level_ ==
MemoryPressureLevel::MEMORY_PRESSURE_LEVEL_MODERATE) {
TRACE_EVENT_NESTABLE_ASYNC_BEGIN0("base",
"MemoryPressure::ModeratePressure", this);
}
if (old_pressure_level != current_pressure_level_) {
delegate_->OnMemoryPressureLevelChanged(current_pressure_level_);
}
}
void MemoryPressureVoteAggregator::NotifyListeners() {
delegate_->OnNotifyListenersRequested();
}
base::MemoryPressureListener::MemoryPressureLevel
MemoryPressureVoteAggregator::EvaluateVotes() const {
DCHECK_CALLED_ON_VALID_SEQUENCE(sequence_checker_);
static_assert(
base::MemoryPressureListener::MEMORY_PRESSURE_LEVEL_CRITICAL == 2,
"Ensure that each memory pressure level is handled by this method.");
if (votes_[2]) {
return base::MemoryPressureListener::MEMORY_PRESSURE_LEVEL_CRITICAL;
}
if (votes_[1]) {
return base::MemoryPressureListener::MEMORY_PRESSURE_LEVEL_MODERATE;
}
return base::MemoryPressureListener::MEMORY_PRESSURE_LEVEL_NONE;
}
void MemoryPressureVoteAggregator::SetVotesForTesting(size_t none_votes,
size_t moderate_votes,
size_t critical_votes) {
DCHECK_CALLED_ON_VALID_SEQUENCE(sequence_checker_);
votes_[0] = none_votes;
votes_[1] = moderate_votes;
votes_[2] = critical_votes;
}
} // namespace memory_pressure
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