pfs_histogram.cc

/* Copyright (c) 2016, 2025, Oracle and/or its affiliates.

  This program is free software; you can redistribute it and/or modify
  it under the terms of the GNU General Public License, version 2.0,
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  This program is distributed in the hope that it will be useful,
  but WITHOUT ANY WARRANTY; without even the implied warranty of
  MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
  GNU General Public License, version 2.0, for more details.

  You should have received a copy of the GNU General Public License
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  Foundation, Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301  USA */

/**
  @file storage/perfschema/pfs_histogram.cc
  Miscellaneous global dependencies (implementation).
*/

#include "storage/perfschema/pfs_histogram.h"

/**
  Histogram base bucket timer, in picoseconds.
  Currently defined as 10 micro second.
*/
#define BUCKET_BASE_TIMER (10 * 1000 * 1000)

/**
  Bucket factor.
  histogram_timer[i+1] = BUCKET_BASE_FACTOR * histogram_timer[i]
  The value is chosen so that BUCKET_BASE_FACTOR ^ 50 = 10,
  which corresponds to a 4.7 percent increase for each bucket,
  or a power of 10 increase for 50 buckets.
*/
#define BUCKET_BASE_FACTOR 1.0471285480508996

/**
  Timer values used in histograms.
  Timer values are expressed in picoseconds.

  timer[0] = 0
  timer[1] = BUCKET_BASE_TIMER

  From then,
  timer[N+1] = BUCKET_BASE_FACTOR * timer[N]

  The last timer is set to infinity.
*/
PFS_histogram_timers g_histogram_pico_timers;

void PFS_histogram::reset() {
  ulong bucket_index;

  for (bucket_index = 0; bucket_index < NUMBER_OF_BUCKETS; bucket_index++) {
    m_bucket[bucket_index] = 0;
  }
}

void PFS_histogram_timers::init() {
  ulong bucket_index;
  double current_bucket_timer = BUCKET_BASE_TIMER;

  m_bucket_timer[0] = 0;

  for (bucket_index = 1; bucket_index < NUMBER_OF_BUCKETS; bucket_index++) {
    m_bucket_timer[bucket_index] = current_bucket_timer;
    current_bucket_timer *= BUCKET_BASE_FACTOR;
  }

  m_bucket_timer[NUMBER_OF_BUCKETS] = UINT64_MAX;
}