ceph/src/rocksdb/util/stop_watch.h

   1 //  Copyright (c) 2011-present, Facebook, Inc.  All rights reserved.
   2 //  This source code is licensed under both the GPLv2 (found in the
   3 //  COPYING file in the root directory) and Apache 2.0 License
   4 //  (found in the LICENSE.Apache file in the root directory).
   5 //
   6 #pragma once
   7 #include "monitoring/statistics.h"
   8 #include "rocksdb/env.h"
   9
  10 namespace rocksdb {
  11 // Auto-scoped.
  12 // Records the measure time into the corresponding histogram if statistics
  13 // is not nullptr. It is also saved into *elapsed if the pointer is not nullptr
  14 // and overwrite is true, it will be added to *elapsed if overwrite is false.
  15 class StopWatch {
  16  public:
  17   StopWatch(Env* const env, Statistics* statistics, const uint32_t hist_type,
  18             uint64_t* elapsed = nullptr, bool overwrite = true,
  19             bool delay_enabled = false)
  20       : env_(env),
  21         statistics_(statistics),
  22         hist_type_(hist_type),
  23         elapsed_(elapsed),
  24         overwrite_(overwrite),
  25         stats_enabled_(statistics &&
  26                        statistics->get_stats_level() >=
  27                            StatsLevel::kExceptTimers &&
  28                        statistics->HistEnabledForType(hist_type)),
  29         delay_enabled_(delay_enabled),
  30         total_delay_(0),
  31         delay_start_time_(0),
  32         start_time_((stats_enabled_ || elapsed != nullptr) ? env->NowMicros()
  33                                                            : 0) {}
  34
  35   ~StopWatch() {
  36     if (elapsed_) {
  37       if (overwrite_) {
  38         *elapsed_ = env_->NowMicros() - start_time_;
  39       } else {
  40         *elapsed_ += env_->NowMicros() - start_time_;
  41       }
  42     }
  43     if (elapsed_ && delay_enabled_) {
  44       *elapsed_ -= total_delay_;
  45     }
  46     if (stats_enabled_) {
  47       statistics_->reportTimeToHistogram(
  48           hist_type_, (elapsed_ != nullptr)
  49                           ? *elapsed_
  50                           : (env_->NowMicros() - start_time_));
  51     }
  52   }
  53
  54   void DelayStart() {
  55     // if delay_start_time_ is not 0, it means we are already tracking delay,
  56     // so delay_start_time_ should not be overwritten
  57     if (elapsed_ && delay_enabled_ && delay_start_time_ == 0) {
  58       delay_start_time_ = env_->NowMicros();
  59     }
  60   }
  61
  62   void DelayStop() {
  63     if (elapsed_ && delay_enabled_ && delay_start_time_ != 0) {
  64       total_delay_ += env_->NowMicros() - delay_start_time_;
  65     }
  66     // reset to 0 means currently no delay is being tracked, so two consecutive
  67     // calls to DelayStop will not increase total_delay_
  68     delay_start_time_ = 0;
  69   }
  70
  71   uint64_t GetDelay() const { return delay_enabled_ ? total_delay_ : 0; }
  72
  73   uint64_t start_time() const { return start_time_; }
  74
  75  private:
  76   Env* const env_;
  77   Statistics* statistics_;
  78   const uint32_t hist_type_;
  79   uint64_t* elapsed_;
  80   bool overwrite_;
  81   bool stats_enabled_;
  82   bool delay_enabled_;
  83   uint64_t total_delay_;
  84   uint64_t delay_start_time_;
  85   const uint64_t start_time_;
  86 };
  87
  88 // a nano second precision stopwatch
  89 class StopWatchNano {
  90  public:
  91   explicit StopWatchNano(Env* const env, bool auto_start = false)
  92       : env_(env), start_(0) {
  93     if (auto_start) {
  94       Start();
  95     }
  96   }
  97
  98   void Start() { start_ = env_->NowNanos(); }
  99
 100   uint64_t ElapsedNanos(bool reset = false) {
 101     auto now = env_->NowNanos();
 102     auto elapsed = now - start_;
 103     if (reset) {
 104       start_ = now;
 105     }
 106     return elapsed;
 107   }
 108
 109   uint64_t ElapsedNanosSafe(bool reset = false) {
 110     return (env_ != nullptr) ? ElapsedNanos(reset) : 0U;
 111   }
 112
 113  private:
 114   Env* const env_;
 115   uint64_t start_;
 116 };
 117
 118 } // namespace rocksdb