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
18atomic_t fscache_obj_instantiate_histogram[HZ];
19atomic_t fscache_objs_histogram[HZ];
20atomic_t fscache_ops_histogram[HZ];
21atomic_t fscache_retrieval_delay_histogram[HZ];
22atomic_t fscache_retrieval_histogram[HZ];
23
24/*
25 * display the time-taken histogram
26 */
27static 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 */
60static 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 */
72static 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 */
82static void fscache_histogram_stop(struct seq_file *m, void *v)
83{
84}
85
86static 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 */
96static int fscache_histogram_open(struct inode *inode, struct file *file)
97{
98	return seq_open(file, &fscache_histogram_ops);
99}
100
101const 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};
108