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// Copyright 2020 the V8 project 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 "src/heap/cppgc/incremental-marking-schedule.h"
#include <cmath>
#include "src/heap/cppgc/globals.h"
namespace cppgc {
namespace internal {
const double IncrementalMarkingSchedule::kEstimatedMarkingTimeMs = 500.0;
const size_t IncrementalMarkingSchedule::kMinimumMarkedBytesPerIncrementalStep =
64 * kKB;
void IncrementalMarkingSchedule::NotifyIncrementalMarkingStart() {
DCHECK(incremental_marking_start_time_.IsNull());
incremental_marking_start_time_ = v8::base::TimeTicks::Now();
}
void IncrementalMarkingSchedule::UpdateIncrementalMarkedBytes(
size_t overall_marked_bytes) {
DCHECK(!incremental_marking_start_time_.IsNull());
incrementally_marked_bytes_ = overall_marked_bytes;
}
void IncrementalMarkingSchedule::AddConcurrentlyMarkedBytes(
size_t marked_bytes) {
DCHECK(!incremental_marking_start_time_.IsNull());
concurrently_marked_bytes_.fetch_add(marked_bytes, std::memory_order_relaxed);
}
size_t IncrementalMarkingSchedule::GetOverallMarkedBytes() {
return incrementally_marked_bytes_ +
concurrently_marked_bytes_.load(std::memory_order_relaxed);
}
double IncrementalMarkingSchedule::GetElapsedTimeInMs(
v8::base::TimeTicks start_time) {
if (elapsed_time_for_testing_ != kNoSetElapsedTimeForTesting) {
double elapsed_time = elapsed_time_for_testing_;
elapsed_time_for_testing_ = kNoSetElapsedTimeForTesting;
return elapsed_time;
}
return (v8::base::TimeTicks::Now() - start_time).InMillisecondsF();
}
size_t IncrementalMarkingSchedule::GetNextIncrementalStepDuration(
size_t estimated_live_bytes) {
DCHECK(!incremental_marking_start_time_.IsNull());
double elapsed_time_in_ms =
GetElapsedTimeInMs(incremental_marking_start_time_);
size_t actual_marked_bytes = GetOverallMarkedBytes();
size_t expected_marked_bytes = std::ceil(
estimated_live_bytes * elapsed_time_in_ms / kEstimatedMarkingTimeMs);
if (expected_marked_bytes < actual_marked_bytes) {
// Marking is ahead of schedule, incremental marking should do the minimum.
return kMinimumMarkedBytesPerIncrementalStep;
}
// Assuming marking will take |kEstimatedMarkingTime|, overall there will
// be |estimated_live_bytes| live bytes to mark, and that marking speed is
// constant, after |elapsed_time| the number of marked_bytes should be
// |estimated_live_bytes| * (|elapsed_time| / |kEstimatedMarkingTime|),
// denoted as |expected_marked_bytes|. If |actual_marked_bytes| is less,
// i.e. marking is behind schedule, incremental marking should help "catch
// up" by marking (|expected_marked_bytes| - |actual_marked_bytes|).
return std::max(kMinimumMarkedBytesPerIncrementalStep,
expected_marked_bytes - actual_marked_bytes);
}
} // namespace internal
} // namespace cppgc
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