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  RETRV DLY RETRIEVLS\n");
  35                 return 0;
  36         case 2:
  37                 seq_puts(m, "===== ===== ========= ========= ========= ========= =========\n");
  38                 return 0;
  39         default:
  40                 index = (unsigned long) v - 3;
  41                 n[0] = atomic_read(&fscache_obj_instantiate_histogram[index]);
  42                 n[1] = atomic_read(&fscache_ops_histogram[index]);
  43                 n[2] = atomic_read(&fscache_objs_histogram[index]);
  44                 n[3] = atomic_read(&fscache_retrieval_delay_histogram[index]);
  45                 n[4] = atomic_read(&fscache_retrieval_histogram[index]);
  46                 if (!(n[0] | n[1] | n[2] | n[3] | n[4]))
  47                         return 0;
  48
  49                 t = (index * 1000) / HZ;
  50
  51                 seq_printf(m, "%4lu  0.%03u %9u %9u %9u %9u %9u\n",
  52                            index, t, n[0], n[1], n[2], n[3], n[4]);
  53                 return 0;
  54         }
  55 }
  56
  57 /*
  58  * set up the iterator to start reading from the first line
  59  */
  60 static void *fscache_histogram_start(struct seq_file *m, loff_t *_pos)
  61 {
  62         if ((unsigned long long)*_pos >= HZ + 2)
  63                 return NULL;
  64         if (*_pos == 0)
  65                 *_pos = 1;
  66         return (void *)(unsigned long) *_pos;
  67 }
  68
  69 /*
  70  * move to the next line
  71  */
  72 static void *fscache_histogram_next(struct seq_file *m, void *v, loff_t *pos)
  73 {
  74         (*pos)++;
  75         return (unsigned long long)*pos > HZ + 2 ?
  76                 NULL : (void *)(unsigned long) *pos;
  77 }
  78
  79 /*
  80  * clean up after reading
  81  */
  82 static void fscache_histogram_stop(struct seq_file *m, void *v)
  83 {
  84 }
  85
  86 static const struct seq_operations fscache_histogram_ops = {
  87         .start          = fscache_histogram_start,
  88         .stop           = fscache_histogram_stop,
  89         .next           = fscache_histogram_next,
  90         .show           = fscache_histogram_show,
  91 };
  92
  93 /*
  94  * open "/proc/fs/fscache/histogram" to provide latency data
  95  */
  96 static int fscache_histogram_open(struct inode *inode, struct file *file)
  97 {
  98         return seq_open(file, &fscache_histogram_ops);
  99 }
 100
 101 const struct file_operations fscache_histogram_fops = {
 102         .owner          = THIS_MODULE,
 103         .open           = fscache_histogram_open,
 104         .read           = seq_read,
 105         .llseek         = seq_lseek,
 106         .release        = seq_release,
 107 };