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// Copyright 2015 The Chromium Authors
// Use of this source code is governed by a BSD-style license that can be
// found in the LICENSE file.
#include "content/browser/cache_storage/cache_storage_scheduler.h"
#include <string>
#include "base/check_op.h"
#include "base/feature_list.h"
#include "base/functional/bind.h"
#include "base/functional/callback_helpers.h"
#include "base/location.h"
#include "base/metrics/field_trial_params.h"
#include "base/metrics/histogram_macros.h"
#include "base/task/sequenced_task_runner.h"
#include "build/build_config.h"
#include "content/browser/cache_storage/cache_storage_histogram_utils.h"
#include "content/browser/cache_storage/cache_storage_operation.h"
namespace content {
namespace {
// Maximum parallel shared operations. This constant was selected via
// experimentation. We tried 4, 16, and 64 for the limit. 16 was clearly
// better than 4, but 64 was did not provide significant further benefit.
constexpr int kDefaultMaxSharedOps = 16;
const base::FeatureParam<int> kCacheStorageMaxSharedOps{
&kCacheStorageParallelOps, "max_shared_ops", kDefaultMaxSharedOps};
bool OpPointerLessThan(const std::unique_ptr<CacheStorageOperation>& left,
const std::unique_ptr<CacheStorageOperation>& right) {
DCHECK(left);
DCHECK(right);
// We want to prioritize high priority operations, but otherwise sort
// by creation order. Since the first created operations will have a lower
// identifier value we reverse the logic of the id comparison.
//
// Note, there might be a slight mis-ordering when the 64-bit id values
// rollover, but this should not be critical and will happen very rarely.
if (left->priority() < right->priority()) {
return true;
}
if (left->priority() > right->priority()) {
return false;
}
return left->id() > right->id();
}
} // namespace
// Enables support for parallel cache_storage operations via the
// "max_shared_ops" fieldtrial parameter.
BASE_FEATURE(kCacheStorageParallelOps,
"CacheStorageParallelOps",
base::FEATURE_ENABLED_BY_DEFAULT);
CacheStorageScheduler::CacheStorageScheduler(
CacheStorageSchedulerClient client_type,
scoped_refptr<base::SequencedTaskRunner> task_runner)
: task_runner_(std::move(task_runner)), client_type_(client_type) {
std::make_heap(pending_operations_.begin(), pending_operations_.end(),
&OpPointerLessThan);
}
CacheStorageScheduler::~CacheStorageScheduler() {
DCHECK_CALLED_ON_VALID_SEQUENCE(sequence_checker_);
}
CacheStorageSchedulerId CacheStorageScheduler::CreateId() {
DCHECK_CALLED_ON_VALID_SEQUENCE(sequence_checker_);
return next_id_++;
}
void CacheStorageScheduler::ScheduleOperation(
CacheStorageSchedulerId id,
CacheStorageSchedulerMode mode,
CacheStorageSchedulerOp op_type,
CacheStorageSchedulerPriority priority,
base::OnceClosure closure) {
DCHECK_CALLED_ON_VALID_SEQUENCE(sequence_checker_);
RecordCacheStorageSchedulerUMA(CacheStorageSchedulerUMA::kQueueLength,
client_type_, op_type,
pending_operations_.size());
pending_operations_.push_back(std::make_unique<CacheStorageOperation>(
std::move(closure), id, client_type_, mode, op_type, priority,
task_runner_));
std::push_heap(pending_operations_.begin(), pending_operations_.end(),
&OpPointerLessThan);
MaybeRunOperation();
}
void CacheStorageScheduler::CompleteOperationAndRunNext(
CacheStorageSchedulerId id) {
DCHECK_CALLED_ON_VALID_SEQUENCE(sequence_checker_);
auto it = running_operations_.find(id);
CHECK(it != running_operations_.end());
DCHECK_EQ(it->second->id(), id);
if (it->second->mode() == CacheStorageSchedulerMode::kShared) {
DCHECK_EQ(num_running_exclusive_, 0);
DCHECK_GT(num_running_shared_, 0);
num_running_shared_ -= 1;
} else {
DCHECK_EQ(num_running_shared_, 0);
DCHECK_EQ(num_running_exclusive_, 1);
num_running_exclusive_ -= 1;
}
running_operations_.erase(it);
MaybeRunOperation();
}
bool CacheStorageScheduler::ScheduledOperations() const {
DCHECK_CALLED_ON_VALID_SEQUENCE(sequence_checker_);
return !running_operations_.empty() || !pending_operations_.empty();
}
bool CacheStorageScheduler::IsRunningExclusiveOperation() const {
DCHECK_CALLED_ON_VALID_SEQUENCE(sequence_checker_);
return num_running_exclusive_ > 0;
}
void CacheStorageScheduler::DispatchOperationTask(base::OnceClosure task) {
DCHECK_CALLED_ON_VALID_SEQUENCE(sequence_checker_);
std::move(task).Run();
}
void CacheStorageScheduler::MaybeRunOperation() {
DCHECK_CALLED_ON_VALID_SEQUENCE(sequence_checker_);
// Most operations are wrapped with `CompleteOperationAndRunNext()`, which
// means that executing an operation can cause re-entrancy in
// `MaybeRunOperation().` No-op in this case; the next operation will be run
// in the next loop iteration. Note that this doesn't use `AutoReset` because
// running an operation can cause `this` to be deleted. See
// https://crbug.com/370069678.
if (in_maybe_run_) {
return;
}
in_maybe_run_ = true;
base::WeakPtr<CacheStorageScheduler> this_ptr =
weak_ptr_factory_.GetWeakPtr();
base::ScopedClosureRunner reset(base::BindOnce(
[](base::WeakPtr<CacheStorageScheduler> scheduler) {
if (scheduler) {
scheduler->in_maybe_run_ = false;
}
},
this_ptr));
while (this_ptr && !pending_operations_.empty()) {
base::WeakPtr<CacheStorageOperation> next_operation =
pending_operations_.front()->AsWeakPtr();
// Determine if we can run the next operation based on its mode
// and the current state of executing operations. We allow multiple
// kShared operations to run in parallel, but a kExclusive operation
// must not overlap with any other operation.
if (num_running_exclusive_ > 0) {
return;
}
const bool is_shared_op =
next_operation->mode() == CacheStorageSchedulerMode::kShared;
const int max_concurrent_ops =
is_shared_op ? kCacheStorageMaxSharedOps.Get() : 1;
if (num_running_shared_ >= max_concurrent_ops) {
return;
}
running_operations_.emplace(next_operation->id(),
std::move(pending_operations_.front()));
std::pop_heap(pending_operations_.begin(), pending_operations_.end(),
&OpPointerLessThan);
pending_operations_.pop_back();
RecordCacheStorageSchedulerUMA(
CacheStorageSchedulerUMA::kQueueDuration, client_type_,
next_operation->op_type(),
base::TimeTicks::Now() - next_operation->creation_ticks());
if (is_shared_op) {
CHECK_EQ(num_running_exclusive_, 0);
num_running_shared_ += 1;
} else {
CHECK_EQ(num_running_exclusive_, 0);
CHECK_EQ(num_running_shared_, 0);
num_running_exclusive_ += 1;
}
DispatchOperationTask(
base::BindOnce(&CacheStorageOperation::Run, next_operation));
// `next_operation` and `this_ptr` may both be null at this point.
}
}
} // namespace content
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