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
44 lines
1.1 KiB
C++
44 lines
1.1 KiB
C++
// Copyright (c) 2014, 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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#include <sstream>
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#include "rocksdb/env.h"
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#include "util/iostats_context_imp.h"
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namespace rocksdb {
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#ifndef IOS_CROSS_COMPILE
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__thread IOStatsContext iostats_context;
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#endif // IOS_CROSS_COMPILE
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void IOStatsContext::Reset() {
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thread_pool_id = Env::Priority::TOTAL;
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bytes_read = 0;
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bytes_written = 0;
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open_nanos = 0;
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allocate_nanos = 0;
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write_nanos = 0;
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range_sync_nanos = 0;
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logger_nanos = 0;
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}
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#define OUTPUT(counter) #counter << " = " << counter << ", "
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std::string IOStatsContext::ToString() const {
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std::ostringstream ss;
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ss << OUTPUT(thread_pool_id)
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<< OUTPUT(bytes_read)
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<< OUTPUT(bytes_written)
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<< OUTPUT(open_nanos)
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<< OUTPUT(allocate_nanos)
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<< OUTPUT(write_nanos)
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<< OUTPUT(range_sync_nanos)
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<< OUTPUT(logger_nanos);
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return ss.str();
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}
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} // namespace rocksdb
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