fs/fscache/histogram.c

   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
  14 atomic_t fscache_obj_instantiate_histogram[HZ];
  15 atomic_t fscache_objs_histogram[HZ];
  16 atomic_t fscache_ops_histogram[HZ];
  17 atomic_t fscache_retrieval_delay_histogram[HZ];
  18 atomic_t fscache_retrieval_histogram[HZ];
  19
  20 /*
  21  * display the time-taken histogram
  22  */
  23 static 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  */
  56 static 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  */
  68 static 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  */
  78 static void fscache_histogram_stop(struct seq_file *m, void *v)
  79 {
  80 }
  81
  82 const 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 };