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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
27 lines
635 B
C++
27 lines
635 B
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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#include <sstream>
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#include "util/perf_level_imp.h"
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namespace rocksdb {
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#if defined(IOS_CROSS_COMPILE)
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PerfLevel perf_level = kEnableCount;
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#else
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__thread PerfLevel perf_level = kEnableCount;
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#endif
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void SetPerfLevel(PerfLevel level) {
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perf_level = level;
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}
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PerfLevel GetPerfLevel() {
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return perf_level;
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}
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} // namespace rocksdb
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