dbe3810c74
Summary: Context: As need for new feature of resource management using RocksDB's rate limiter like [https://github.com/facebook/rocksdb/issues/8595](https://github.com/facebook/rocksdb/pull/8595) arises, it is about time to re-learn our rate limiter and make this learning process easier for others by improving its readability. The comment/assertion/one extra else-branch are added based on my best understanding toward the rate_limiter.cc and rate_limiter_test.cc up to date after giving it a hard read. - Add code comments/assertion/one extra else-branch (that is not affecting existing behavior, see PR comment) to describe how leader-election works under multi-thread settings in GenericRateLimiter::Request() - Add code comments to describe a non-obvious trick during clean-up of rate limiter destructor - Add code comments to explain more about the starvation being fixed in GenericRateLimiter::Refill() through partial byte-granting - Add code comments to the rate limiter's setup in a complicated unit test in rate_limiter_test Pull Request resolved: https://github.com/facebook/rocksdb/pull/8596 Test Plan: - passed existing rate_limiter_test.cc Reviewed By: ajkr Differential Revision: D29982590 Pulled By: hx235 fbshipit-source-id: c3592986bb5b0c90d8229fe44f425251ec7e8a0a
115 lines
3.4 KiB
C++
115 lines
3.4 KiB
C++
// Copyright (c) 2011-present, Facebook, Inc. All rights reserved.
|
|
// This source code is licensed under both the GPLv2 (found in the
|
|
// COPYING file in the root directory) and Apache 2.0 License
|
|
// (found in the LICENSE.Apache file in the root directory).
|
|
//
|
|
// Copyright (c) 2011 The LevelDB Authors. All rights reserved.
|
|
// Use of this source code is governed by a BSD-style license that can be
|
|
// found in the LICENSE file. See the AUTHORS file for names of contributors.
|
|
|
|
#pragma once
|
|
|
|
#include <algorithm>
|
|
#include <atomic>
|
|
#include <chrono>
|
|
#include <deque>
|
|
|
|
#include "port/port.h"
|
|
#include "rocksdb/env.h"
|
|
#include "rocksdb/rate_limiter.h"
|
|
#include "rocksdb/system_clock.h"
|
|
#include "util/mutexlock.h"
|
|
#include "util/random.h"
|
|
|
|
namespace ROCKSDB_NAMESPACE {
|
|
|
|
class GenericRateLimiter : public RateLimiter {
|
|
public:
|
|
GenericRateLimiter(int64_t refill_bytes, int64_t refill_period_us,
|
|
int32_t fairness, RateLimiter::Mode mode,
|
|
const std::shared_ptr<SystemClock>& clock,
|
|
bool auto_tuned);
|
|
|
|
virtual ~GenericRateLimiter();
|
|
|
|
// This API allows user to dynamically change rate limiter's bytes per second.
|
|
virtual void SetBytesPerSecond(int64_t bytes_per_second) override;
|
|
|
|
// Request for token to write bytes. If this request can not be satisfied,
|
|
// the call is blocked. Caller is responsible to make sure
|
|
// bytes <= GetSingleBurstBytes()
|
|
using RateLimiter::Request;
|
|
virtual void Request(const int64_t bytes, const Env::IOPriority pri,
|
|
Statistics* stats) override;
|
|
|
|
virtual int64_t GetSingleBurstBytes() const override {
|
|
return refill_bytes_per_period_.load(std::memory_order_relaxed);
|
|
}
|
|
|
|
virtual int64_t GetTotalBytesThrough(
|
|
const Env::IOPriority pri = Env::IO_TOTAL) const override {
|
|
MutexLock g(&request_mutex_);
|
|
if (pri == Env::IO_TOTAL) {
|
|
return total_bytes_through_[Env::IO_LOW] +
|
|
total_bytes_through_[Env::IO_HIGH];
|
|
}
|
|
return total_bytes_through_[pri];
|
|
}
|
|
|
|
virtual int64_t GetTotalRequests(
|
|
const Env::IOPriority pri = Env::IO_TOTAL) const override {
|
|
MutexLock g(&request_mutex_);
|
|
if (pri == Env::IO_TOTAL) {
|
|
return total_requests_[Env::IO_LOW] + total_requests_[Env::IO_HIGH];
|
|
}
|
|
return total_requests_[pri];
|
|
}
|
|
|
|
virtual int64_t GetBytesPerSecond() const override {
|
|
return rate_bytes_per_sec_;
|
|
}
|
|
|
|
private:
|
|
void RefillBytesAndGrantRequests();
|
|
int64_t CalculateRefillBytesPerPeriod(int64_t rate_bytes_per_sec);
|
|
Status Tune();
|
|
|
|
uint64_t NowMicrosMonotonic() { return clock_->NowNanos() / std::milli::den; }
|
|
|
|
// This mutex guard all internal states
|
|
mutable port::Mutex request_mutex_;
|
|
|
|
const int64_t kMinRefillBytesPerPeriod = 100;
|
|
|
|
const int64_t refill_period_us_;
|
|
|
|
int64_t rate_bytes_per_sec_;
|
|
// This variable can be changed dynamically.
|
|
std::atomic<int64_t> refill_bytes_per_period_;
|
|
std::shared_ptr<SystemClock> clock_;
|
|
|
|
bool stop_;
|
|
port::CondVar exit_cv_;
|
|
int32_t requests_to_wait_;
|
|
|
|
int64_t total_requests_[Env::IO_TOTAL];
|
|
int64_t total_bytes_through_[Env::IO_TOTAL];
|
|
int64_t available_bytes_;
|
|
int64_t next_refill_us_;
|
|
|
|
int32_t fairness_;
|
|
Random rnd_;
|
|
|
|
struct Req;
|
|
Req* leader_;
|
|
std::deque<Req*> queue_[Env::IO_TOTAL];
|
|
|
|
bool auto_tuned_;
|
|
int64_t num_drains_;
|
|
int64_t prev_num_drains_;
|
|
const int64_t max_bytes_per_sec_;
|
|
std::chrono::microseconds tuned_time_;
|
|
};
|
|
|
|
} // namespace ROCKSDB_NAMESPACE
|