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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.
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// This source code is licensed under the BSD-style license found in the
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// LICENSE file in the root directory of this source tree. An additional grant
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// of patent rights can be found in the PATENTS file in the same directory.
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//
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#pragma once
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#include "rocksdb/env.h"
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#include "util/perf_level_imp.h"
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#include "util/stop_watch.h"
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namespace rocksdb {
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class PerfStepTimer {
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public:
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PerfStepTimer(uint64_t* metric)
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: enabled_(perf_level >= PerfLevel::kEnableTime),
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env_(enabled_ ? Env::Default() : nullptr),
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start_(0),
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metric_(metric) {
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}
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~PerfStepTimer() {
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Stop();
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}
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void Start() {
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if (enabled_) {
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start_ = env_->NowNanos();
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}
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}
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void Measure() {
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if (start_) {
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uint64_t now = env_->NowNanos();
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*metric_ += now - start_;
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start_ = now;
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}
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}
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void Stop() {
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if (start_) {
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*metric_ += env_->NowNanos() - start_;
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start_ = 0;
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}
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}
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private:
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const bool enabled_;
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Env* const env_;
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uint64_t start_;
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uint64_t* metric_;
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};
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} // namespace rocksdb
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