linux/fs/fscache/histogram.c
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   1// SPDX-License-Identifier: GPL-2.0-or-later
   2/* FS-Cache latency histogram
   3 *
   4 * Copyright (C) 2008 Red Hat, Inc. All Rights Reserved.
   5 * Written by David Howells (dhowells@redhat.com)
   6 */
   7
   8#define FSCACHE_DEBUG_LEVEL THREAD
   9#include <linux/module.h>
  10#include <linux/proc_fs.h>
  11#include <linux/seq_file.h>
  12#include "internal.h"
  13
  14atomic_t fscache_obj_instantiate_histogram[HZ];
  15atomic_t fscache_objs_histogram[HZ];
  16atomic_t fscache_ops_histogram[HZ];
  17atomic_t fscache_retrieval_delay_histogram[HZ];
  18atomic_t fscache_retrieval_histogram[HZ];
  19
  20/*
  21 * display the time-taken histogram
  22 */
  23static int fscache_histogram_show(struct seq_file *m, void *v)
  24{
  25        unsigned long index;
  26        unsigned n[5], t;
  27
  28        switch ((unsigned long) v) {
  29        case 1:
  30                seq_puts(m, "JIFS  SECS  OBJ INST  OP RUNS   OBJ RUNS  RETRV DLY RETRIEVLS\n");
  31                return 0;
  32        case 2:
  33                seq_puts(m, "===== ===== ========= ========= ========= ========= =========\n");
  34                return 0;
  35        default:
  36                index = (unsigned long) v - 3;
  37                n[0] = atomic_read(&fscache_obj_instantiate_histogram[index]);
  38                n[1] = atomic_read(&fscache_ops_histogram[index]);
  39                n[2] = atomic_read(&fscache_objs_histogram[index]);
  40                n[3] = atomic_read(&fscache_retrieval_delay_histogram[index]);
  41                n[4] = atomic_read(&fscache_retrieval_histogram[index]);
  42                if (!(n[0] | n[1] | n[2] | n[3] | n[4]))
  43                        return 0;
  44
  45                t = (index * 1000) / HZ;
  46
  47                seq_printf(m, "%4lu  0.%03u %9u %9u %9u %9u %9u\n",
  48                           index, t, n[0], n[1], n[2], n[3], n[4]);
  49                return 0;
  50        }
  51}
  52
  53/*
  54 * set up the iterator to start reading from the first line
  55 */
  56static void *fscache_histogram_start(struct seq_file *m, loff_t *_pos)
  57{
  58        if ((unsigned long long)*_pos >= HZ + 2)
  59                return NULL;
  60        if (*_pos == 0)
  61                *_pos = 1;
  62        return (void *)(unsigned long) *_pos;
  63}
  64
  65/*
  66 * move to the next line
  67 */
  68static void *fscache_histogram_next(struct seq_file *m, void *v, loff_t *pos)
  69{
  70        (*pos)++;
  71        return (unsigned long long)*pos > HZ + 2 ?
  72                NULL : (void *)(unsigned long) *pos;
  73}
  74
  75/*
  76 * clean up after reading
  77 */
  78static void fscache_histogram_stop(struct seq_file *m, void *v)
  79{
  80}
  81
  82const struct seq_operations fscache_histogram_ops = {
  83        .start          = fscache_histogram_start,
  84        .stop           = fscache_histogram_stop,
  85        .next           = fscache_histogram_next,
  86        .show           = fscache_histogram_show,
  87};
  88