mirror of
https://github.com/facebook/rocksdb.git
synced 2024-11-26 16:30:56 +00:00
ec7a944360
Summary: We occasionally get write stalls (>1s Write() calls) on HDD under read load. The following timers explain almost all of the stalls: - perf_context.db_mutex_lock_nanos - perf_context.db_condition_wait_nanos - iostats_context.open_time - iostats_context.allocate_time - iostats_context.write_time - iostats_context.range_sync_time - iostats_context.logger_time In my experiments each of these occasionally takes >1s on write path under some workload. There are rare cases when Write() takes long but none of these takes long. Test Plan: Added code to our application to write the listed timings to log for slow writes. They usually add up to almost exactly the time Write() call took. Reviewers: rven, yhchiang, sdong Reviewed By: sdong Subscribers: march, dhruba, tnovak Differential Revision: https://reviews.facebook.net/D39177
55 lines
1.1 KiB
C++
55 lines
1.1 KiB
C++
// Copyright (c) 2013, Facebook, Inc. All rights reserved.
|
|
// This source code is licensed under the BSD-style license found in the
|
|
// LICENSE file in the root directory of this source tree. An additional grant
|
|
// of patent rights can be found in the PATENTS file in the same directory.
|
|
//
|
|
#pragma once
|
|
#include "rocksdb/env.h"
|
|
#include "util/perf_level_imp.h"
|
|
#include "util/stop_watch.h"
|
|
|
|
namespace rocksdb {
|
|
|
|
class PerfStepTimer {
|
|
public:
|
|
PerfStepTimer(uint64_t* metric)
|
|
: enabled_(perf_level >= PerfLevel::kEnableTime),
|
|
env_(enabled_ ? Env::Default() : nullptr),
|
|
start_(0),
|
|
metric_(metric) {
|
|
}
|
|
|
|
~PerfStepTimer() {
|
|
Stop();
|
|
}
|
|
|
|
void Start() {
|
|
if (enabled_) {
|
|
start_ = env_->NowNanos();
|
|
}
|
|
}
|
|
|
|
void Measure() {
|
|
if (start_) {
|
|
uint64_t now = env_->NowNanos();
|
|
*metric_ += now - start_;
|
|
start_ = now;
|
|
}
|
|
}
|
|
|
|
void Stop() {
|
|
if (start_) {
|
|
*metric_ += env_->NowNanos() - start_;
|
|
start_ = 0;
|
|
}
|
|
}
|
|
|
|
private:
|
|
const bool enabled_;
|
|
Env* const env_;
|
|
uint64_t start_;
|
|
uint64_t* metric_;
|
|
};
|
|
|
|
} // namespace rocksdb
|