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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.
#ifndef V8_HEAP_CPPGC_DEFAULT_JOB_H_
#define V8_HEAP_CPPGC_DEFAULT_JOB_H_
#include <atomic>
#include <map>
#include <memory>
#include <unordered_set>
#include <vector>
#include "include/cppgc/platform.h"
#include "src/base/logging.h"
#include "src/base/platform/mutex.h"
namespace cppgc {
namespace internal {
template <typename Job>
class DefaultJobFactory {
public:
static std::shared_ptr<Job> Create(std::unique_ptr<cppgc::JobTask> job_task) {
std::shared_ptr<Job> job =
std::make_shared<Job>(typename Job::Key(), std::move(job_task));
job->NotifyConcurrencyIncrease();
return job;
}
};
template <typename Thread>
class DefaultJobImpl {
public:
class JobDelegate;
class JobHandle;
class Key {
private:
Key() {}
template <typename Job>
friend class DefaultJobFactory;
};
DefaultJobImpl(Key, std::unique_ptr<cppgc::JobTask> job_task)
: job_task_(std::move(job_task)) {}
~DefaultJobImpl() {
Cancel();
DCHECK_EQ(0, active_threads_.load(std::memory_order_relaxed));
}
void NotifyConcurrencyIncrease();
void Join() {
for (std::shared_ptr<Thread>& thread : job_threads_) thread->Join();
job_threads_.clear();
can_run_.store(false, std::memory_order_relaxed);
}
void Cancel() {
can_run_.store(false, std::memory_order_relaxed);
Join();
}
bool IsCompleted() const { return !IsRunning(); }
bool IsRunning() const {
uint8_t active_threads = active_threads_.load(std::memory_order_relaxed);
return (active_threads + job_task_->GetMaxConcurrency(active_threads)) > 0;
}
bool CanRun() const { return can_run_.load(std::memory_order_relaxed); }
void RunJobTask() {
DCHECK_NOT_NULL(job_task_);
NotifyJobThreadStart();
JobDelegate delegate(this);
job_task_->Run(&delegate);
NotifyJobThreadEnd();
}
protected:
virtual std::shared_ptr<Thread> CreateThread(DefaultJobImpl*) = 0;
void NotifyJobThreadStart() {
active_threads_.fetch_add(1, std::memory_order_relaxed);
}
void NotifyJobThreadEnd() {
active_threads_.fetch_sub(1, std::memory_order_relaxed);
}
void GuaranteeAvailableIds(uint8_t max_threads) {
if (max_threads <= highest_thread_count_) return;
v8::base::MutexGuard guard(&ids_lock_);
while (highest_thread_count_ < max_threads) {
available_ids_.push_back(++highest_thread_count_);
}
}
std::unique_ptr<cppgc::JobTask> job_task_;
std::vector<std::shared_ptr<Thread>> job_threads_;
std::atomic_bool can_run_{true};
std::atomic<uint8_t> active_threads_{0};
// Task id management.
v8::base::Mutex ids_lock_;
std::vector<uint8_t> available_ids_;
uint8_t highest_thread_count_ = -1;
};
template <typename Thread>
class DefaultJobImpl<Thread>::JobDelegate final : public cppgc::JobDelegate {
public:
explicit JobDelegate(DefaultJobImpl* job) : job_(job) {}
~JobDelegate() { ReleaseTaskId(); }
bool ShouldYield() override { return !job_->CanRun(); }
void NotifyConcurrencyIncrease() override {
job_->NotifyConcurrencyIncrease();
}
uint8_t GetTaskId() override {
AcquireTaskId();
return job_thread_id_;
}
private:
void AcquireTaskId() {
if (job_thread_id_ != kInvalidTaskId) return;
v8::base::MutexGuard guard(&job_->ids_lock_);
job_thread_id_ = job_->available_ids_.back();
DCHECK_NE(kInvalidTaskId, job_thread_id_);
job_->available_ids_.pop_back();
}
void ReleaseTaskId() {
if (job_thread_id_ == kInvalidTaskId) return;
v8::base::MutexGuard guard(&job_->ids_lock_);
job_->available_ids_.push_back(job_thread_id_);
}
DefaultJobImpl* const job_;
static constexpr uint8_t kInvalidTaskId = std::numeric_limits<uint8_t>::max();
uint8_t job_thread_id_ = kInvalidTaskId;
};
template <typename Thread>
void DefaultJobImpl<Thread>::NotifyConcurrencyIncrease() {
DCHECK(CanRun());
static const size_t kMaxThreads = Thread::GetMaxSupportedConcurrency();
uint8_t current_active_threads =
active_threads_.load(std::memory_order_relaxed);
size_t max_threads = std::min(
kMaxThreads, job_task_->GetMaxConcurrency(current_active_threads));
if (current_active_threads >= max_threads) return;
DCHECK_LT(max_threads, std::numeric_limits<uint8_t>::max());
GuaranteeAvailableIds(max_threads);
for (uint8_t new_threads = max_threads - current_active_threads;
new_threads > 0; --new_threads) {
std::shared_ptr<Thread> thread = CreateThread(this);
job_threads_.push_back(thread);
}
}
template <typename Thread>
class DefaultJobImpl<Thread>::JobHandle final : public cppgc::JobHandle {
public:
explicit JobHandle(std::shared_ptr<DefaultJobImpl> job)
: job_(std::move(job)) {
DCHECK_NOT_NULL(job_);
}
void NotifyConcurrencyIncrease() override {
job_->NotifyConcurrencyIncrease();
}
void Join() override { job_->Join(); }
void Cancel() override { job_->Cancel(); }
bool IsCompleted() override { return job_->IsCompleted(); }
bool IsRunning() override { return job_->IsRunning(); }
private:
std::shared_ptr<DefaultJobImpl> job_;
};
} // namespace internal
} // namespace cppgc
#endif // V8_HEAP_CPPGC_DEFAULT_JOB_H_
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