rocksdb/util/rate_limiter.h
mrambacher 3dff28cf9b Use SystemClock* instead of std::shared_ptr<SystemClock> in lower level routines (#8033)
Summary:
For performance purposes, the lower level routines were changed to use a SystemClock* instead of a std::shared_ptr<SystemClock>.  The shared ptr has some performance degradation on certain hardware classes.

For most of the system, there is no risk of the pointer being deleted/invalid because the shared_ptr will be stored elsewhere.  For example, the ImmutableDBOptions stores the Env which has a std::shared_ptr<SystemClock> in it.  The SystemClock* within the ImmutableDBOptions is essentially a "short cut" to gain access to this constant resource.

There were a few classes (PeriodicWorkScheduler?) where the "short cut" property did not hold.  In those cases, the shared pointer was preserved.

Using db_bench readrandom perf_level=3 on my EC2 box, this change performed as well or better than 6.17:

6.17: readrandom   :      28.046 micros/op 854902 ops/sec;   61.3 MB/s (355999 of 355999 found)
6.18: readrandom   :      32.615 micros/op 735306 ops/sec;   52.7 MB/s (290999 of 290999 found)
PR: readrandom   :      27.500 micros/op 871909 ops/sec;   62.5 MB/s (367999 of 367999 found)

(Note that the times for 6.18 are prior to revert of the SystemClock).

Pull Request resolved: https://github.com/facebook/rocksdb/pull/8033

Reviewed By: pdillinger

Differential Revision: D27014563

Pulled By: mrambacher

fbshipit-source-id: ad0459eba03182e454391b5926bf5cdd45657b67
2021-03-15 04:34:11 -07:00

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 Refill();
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