fs/fscache/histogram.c

   1 /* FS-Cache latency histogram
   2  *
   3  * Copyright (C) 2008 Red Hat, Inc. All Rights Reserved.
   4  * Written by David Howells (dhowells@redhat.com)
   5  *
   6  * This program is free software; you can redistribute it and/or
   7  * modify it under the terms of the GNU General Public Licence
   8  * as published by the Free Software Foundation; either version
   9  * 2 of the Licence, or (at your option) any later version.
  10  */
  11
  12 #define FSCACHE_DEBUG_LEVEL THREAD
  13 #include <linux/module.h>
  14 #include <linux/proc_fs.h>
  15 #include <linux/seq_file.h>
  16 #include "internal.h"
  17
  18 atomic_t fscache_obj_instantiate_histogram[HZ];
  19 atomic_t fscache_objs_histogram[HZ];
  20 atomic_t fscache_ops_histogram[HZ];
  21 atomic_t fscache_retrieval_delay_histogram[HZ];
  22 atomic_t fscache_retrieval_histogram[HZ];
  23
  24 /*
  25  * display the time-taken histogram
  26  */
  27 static int fscache_histogram_show(struct seq_file *m, void *v)
  28 {
  29         unsigned long index;
  30         unsigned n[5], t;
  31
  32         switch ((unsigned long) v) {
  33         case 1:
  34                 seq_puts(m, "JIFS  SECS  OBJ INST  OP RUNS   OBJ RUNS "
  35                          " RETRV DLY RETRIEVLS\n");
  36                 return 0;
  37         case 2:
  38                 seq_puts(m, "===== ===== ========= ========= ========="
  39                          " ========= =========\n");
  40                 return 0;
  41         default:
  42                 index = (unsigned long) v - 3;
  43                 n[0] = atomic_read(&fscache_obj_instantiate_histogram[index]);
  44                 n[1] = atomic_read(&fscache_ops_histogram[index]);
  45                 n[2] = atomic_read(&fscache_objs_histogram[index]);
  46                 n[3] = atomic_read(&fscache_retrieval_delay_histogram[index]);
  47                 n[4] = atomic_read(&fscache_retrieval_histogram[index]);
  48                 if (!(n[0] | n[1] | n[2] | n[3] | n[4]))
  49                         return 0;
  50
  51                 t = (index * 1000) / HZ;
  52
  53                 seq_printf(m, "%4lu  0.%03u %9u %9u %9u %9u %9u\n",
  54                            index, t, n[0], n[1], n[2], n[3], n[4]);
  55                 return 0;
  56         }
  57 }
  58
  59 /*
  60  * set up the iterator to start reading from the first line
  61  */
  62 static void *fscache_histogram_start(struct seq_file *m, loff_t *_pos)
  63 {
  64         if ((unsigned long long)*_pos >= HZ + 2)
  65                 return NULL;
  66         if (*_pos == 0)
  67                 *_pos = 1;
  68         return (void *)(unsigned long) *_pos;
  69 }
  70
  71 /*
  72  * move to the next line
  73  */
  74 static void *fscache_histogram_next(struct seq_file *m, void *v, loff_t *pos)
  75 {
  76         (*pos)++;
  77         return (unsigned long long)*pos > HZ + 2 ?
  78                 NULL : (void *)(unsigned long) *pos;
  79 }
  80
  81 /*
  82  * clean up after reading
  83  */
  84 static void fscache_histogram_stop(struct seq_file *m, void *v)
  85 {
  86 }
  87
  88 static const struct seq_operations fscache_histogram_ops = {
  89         .start          = fscache_histogram_start,
  90         .stop           = fscache_histogram_stop,
  91         .next           = fscache_histogram_next,
  92         .show           = fscache_histogram_show,
  93 };
  94
  95 /*
  96  * open "/proc/fs/fscache/histogram" to provide latency data
  97  */
  98 static int fscache_histogram_open(struct inode *inode, struct file *file)
  99 {
 100         return seq_open(file, &fscache_histogram_ops);
 101 }
 102
 103 const struct file_operations fscache_histogram_fops = {
 104         .owner          = THIS_MODULE,
 105         .open           = fscache_histogram_open,
 106         .read           = seq_read,
 107         .llseek         = seq_lseek,
 108         .release        = seq_release,
 109 };