lib/stopwatch.h

   1 /* Copyright (c) 2017 Red Hat, Inc.
   2  *
   3  * Licensed under the Apache License, Version 2.0 (the "License");
   4  * you may not use this file except in compliance with the License.
   5  * You may obtain a copy of the License at:
   6  *
   7  *     http://www.apache.org/licenses/LICENSE-2.0
   8  *
   9  * Unless required by applicable law or agreed to in writing, software
  10  * distributed under the License is distributed on an "AS IS" BASIS,
  11  * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
  12  * See the License for the specific language governing permissions and
  13  * limitations under the License.
  14  */
  15
  16 #ifndef STOPWATCH_H
  17 #define STOPWATCH_H 1
  18
  19 #include <stdbool.h>
  20
  21 enum stopwatch_units {
  22     SW_MS,
  23     SW_US,
  24     SW_NS,
  25 };
  26
  27 struct stopwatch_stats {
  28     unsigned long long count;    /* Total number of samples. */
  29     enum stopwatch_units unit;   /* Unit of following values. */
  30     unsigned long long max;      /* Maximum value. */
  31     unsigned long long min;      /* Minimum value. */
  32     double pctl_95;              /* 95th percentile. */
  33     double ewma_50;              /* Exponentially weighted moving average
  34                                     (alpha 0.50). */
  35     double ewma_1;               /* Exponentially weighted moving average
  36                                     (alpha 0.01). */
  37 };
  38
  39 /* Create a new stopwatch.
  40  * The "units" are not used for any calculations but are printed when
  41  * statistics are requested.
  42  */
  43 void stopwatch_create(const char *name, enum stopwatch_units units);
  44
  45 /* Start a stopwatch. */
  46 void stopwatch_start(const char *name, unsigned long long ts);
  47
  48 /* Stop a stopwatch. The elapsed time will be used for updating statistics
  49  * for this stopwatch.
  50  */
  51 void stopwatch_stop(const char *name, unsigned long long ts);
  52
  53 /* Retrieve statistics calculated from collected samples */
  54 bool stopwatch_get_stats(const char *name, struct stopwatch_stats *stats);
  55
  56 /* Block until all enqueued samples have been processed. */
  57 void stopwatch_sync(void);
  58
  59 #endif /* stopwatch.h */