rocksdb/monitoring/instrumented_mutex.h
Andrew Kryczka 9983eecdfb Dedicate cacheline for DB mutex (#9637)
Summary:
We found a case of cacheline bouncing due to writers locking/unlocking `mutex_` and readers accessing `block_cache_tracer_`. We discovered it only after the issue was fixed by https://github.com/facebook/rocksdb/issues/9462 shifting the `DBImpl` members such that `mutex_` and `block_cache_tracer_` were naturally placed in separate cachelines in our regression testing setup. This PR forces the cacheline alignment of `mutex_` so we don't accidentally reintroduce the problem.

Pull Request resolved: https://github.com/facebook/rocksdb/pull/9637

Reviewed By: riversand963

Differential Revision: D34502233

Pulled By: ajkr

fbshipit-source-id: 46aa313b7fe83e80c3de254e332b6fb242434c07
2022-02-27 11:36:54 -08:00

125 lines
3.2 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).
#pragma once
#include "monitoring/statistics.h"
#include "port/port.h"
#include "rocksdb/statistics.h"
#include "rocksdb/system_clock.h"
#include "rocksdb/thread_status.h"
#include "util/stop_watch.h"
namespace ROCKSDB_NAMESPACE {
class InstrumentedCondVar;
// A wrapper class for port::Mutex that provides additional layer
// for collecting stats and instrumentation.
class InstrumentedMutex {
public:
explicit InstrumentedMutex(bool adaptive = false)
: mutex_(adaptive), stats_(nullptr), clock_(nullptr), stats_code_(0) {}
explicit InstrumentedMutex(SystemClock* clock, bool adaptive = false)
: mutex_(adaptive), stats_(nullptr), clock_(clock), stats_code_(0) {}
InstrumentedMutex(Statistics* stats, SystemClock* clock, int stats_code,
bool adaptive = false)
: mutex_(adaptive),
stats_(stats),
clock_(clock),
stats_code_(stats_code) {}
void Lock();
void Unlock() {
mutex_.Unlock();
}
void AssertHeld() {
mutex_.AssertHeld();
}
private:
void LockInternal();
friend class InstrumentedCondVar;
port::Mutex mutex_;
Statistics* stats_;
SystemClock* clock_;
int stats_code_;
};
class ALIGN_AS(CACHE_LINE_SIZE) CacheAlignedInstrumentedMutex
: public InstrumentedMutex {
using InstrumentedMutex::InstrumentedMutex;
char padding[(CACHE_LINE_SIZE - sizeof(InstrumentedMutex) % CACHE_LINE_SIZE) %
CACHE_LINE_SIZE] ROCKSDB_FIELD_UNUSED;
};
static_assert(sizeof(CacheAlignedInstrumentedMutex) % CACHE_LINE_SIZE == 0);
// RAII wrapper for InstrumentedMutex
class InstrumentedMutexLock {
public:
explicit InstrumentedMutexLock(InstrumentedMutex* mutex) : mutex_(mutex) {
mutex_->Lock();
}
~InstrumentedMutexLock() {
mutex_->Unlock();
}
private:
InstrumentedMutex* const mutex_;
InstrumentedMutexLock(const InstrumentedMutexLock&) = delete;
void operator=(const InstrumentedMutexLock&) = delete;
};
// RAII wrapper for temporary releasing InstrumentedMutex inside
// InstrumentedMutexLock
class InstrumentedMutexUnlock {
public:
explicit InstrumentedMutexUnlock(InstrumentedMutex* mutex) : mutex_(mutex) {
mutex_->Unlock();
}
~InstrumentedMutexUnlock() { mutex_->Lock(); }
private:
InstrumentedMutex* const mutex_;
InstrumentedMutexUnlock(const InstrumentedMutexUnlock&) = delete;
void operator=(const InstrumentedMutexUnlock&) = delete;
};
class InstrumentedCondVar {
public:
explicit InstrumentedCondVar(InstrumentedMutex* instrumented_mutex)
: cond_(&(instrumented_mutex->mutex_)),
stats_(instrumented_mutex->stats_),
clock_(instrumented_mutex->clock_),
stats_code_(instrumented_mutex->stats_code_) {}
void Wait();
bool TimedWait(uint64_t abs_time_us);
void Signal() {
cond_.Signal();
}
void SignalAll() {
cond_.SignalAll();
}
private:
void WaitInternal();
bool TimedWaitInternal(uint64_t abs_time_us);
port::CondVar cond_;
Statistics* stats_;
SystemClock* clock_;
int stats_code_;
};
} // namespace ROCKSDB_NAMESPACE