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// Copyright 2015 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/scavenge-job.h"
#include "src/base/platform/time.h"
#include "src/execution/isolate.h"
#include "src/execution/vm-state-inl.h"
#include "src/heap/gc-tracer.h"
#include "src/heap/heap-inl.h"
#include "src/heap/heap.h"
#include "src/heap/spaces.h"
#include "src/init/v8.h"
namespace v8 {
namespace internal {
const double ScavengeJob::kMaxAllocationLimitAsFractionOfNewSpace = 0.8;
void ScavengeJob::IdleTask::RunInternal(double deadline_in_seconds) {
VMState<GC> state(isolate());
TRACE_EVENT_CALL_STATS_SCOPED(isolate(), "v8", "V8.Task");
Heap* heap = isolate()->heap();
double deadline_in_ms =
deadline_in_seconds *
static_cast<double>(base::Time::kMillisecondsPerSecond);
double start_ms = heap->MonotonicallyIncreasingTimeInMs();
double idle_time_in_ms = deadline_in_ms - start_ms;
double scavenge_speed_in_bytes_per_ms =
heap->tracer()->ScavengeSpeedInBytesPerMillisecond();
size_t new_space_size = heap->new_space()->Size();
size_t new_space_capacity = heap->new_space()->Capacity();
job_->NotifyIdleTask();
if (ReachedIdleAllocationLimit(scavenge_speed_in_bytes_per_ms, new_space_size,
new_space_capacity)) {
if (EnoughIdleTimeForScavenge(
idle_time_in_ms, scavenge_speed_in_bytes_per_ms, new_space_size)) {
heap->CollectGarbage(NEW_SPACE, GarbageCollectionReason::kIdleTask);
} else {
// Immediately request another idle task that can get larger idle time.
job_->RescheduleIdleTask(heap);
}
}
}
bool ScavengeJob::ReachedIdleAllocationLimit(
double scavenge_speed_in_bytes_per_ms, size_t new_space_size,
size_t new_space_capacity) {
if (scavenge_speed_in_bytes_per_ms == 0) {
scavenge_speed_in_bytes_per_ms = kInitialScavengeSpeedInBytesPerMs;
}
// Set the allocation limit to the number of bytes we can scavenge in an
// average idle task.
double allocation_limit = kAverageIdleTimeMs * scavenge_speed_in_bytes_per_ms;
// Keep the limit smaller than the new space capacity.
allocation_limit =
Min<double>(allocation_limit,
new_space_capacity * kMaxAllocationLimitAsFractionOfNewSpace);
// Adjust the limit to take into account bytes that will be allocated until
// the next check and keep the limit large enough to avoid scavenges in tiny
// new space.
allocation_limit =
Max<double>(allocation_limit - kBytesAllocatedBeforeNextIdleTask,
kMinAllocationLimit);
return allocation_limit <= new_space_size;
}
bool ScavengeJob::EnoughIdleTimeForScavenge(
double idle_time_in_ms, double scavenge_speed_in_bytes_per_ms,
size_t new_space_size) {
if (scavenge_speed_in_bytes_per_ms == 0) {
scavenge_speed_in_bytes_per_ms = kInitialScavengeSpeedInBytesPerMs;
}
return new_space_size <= idle_time_in_ms * scavenge_speed_in_bytes_per_ms;
}
void ScavengeJob::RescheduleIdleTask(Heap* heap) {
// Make sure that we don't reschedule more than one time.
// Otherwise, we might spam the scheduler with idle tasks.
if (!idle_task_rescheduled_) {
ScheduleIdleTask(heap);
idle_task_rescheduled_ = true;
}
}
void ScavengeJob::ScheduleIdleTaskIfNeeded(Heap* heap, int bytes_allocated) {
bytes_allocated_since_the_last_task_ += bytes_allocated;
if (bytes_allocated_since_the_last_task_ >=
static_cast<int>(kBytesAllocatedBeforeNextIdleTask)) {
ScheduleIdleTask(heap);
bytes_allocated_since_the_last_task_ = 0;
idle_task_rescheduled_ = false;
}
}
void ScavengeJob::ScheduleIdleTask(Heap* heap) {
if (!idle_task_pending_ && !heap->IsTearingDown()) {
v8::Isolate* isolate = reinterpret_cast<v8::Isolate*>(heap->isolate());
if (V8::GetCurrentPlatform()->IdleTasksEnabled(isolate)) {
idle_task_pending_ = true;
auto task = base::make_unique<IdleTask>(heap->isolate(), this);
V8::GetCurrentPlatform()->GetForegroundTaskRunner(isolate)->PostIdleTask(
std::move(task));
}
}
}
} // namespace internal
} // namespace v8
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