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 "
 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 */
 62static 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 */
 74static 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 */
 84static void fscache_histogram_stop(struct seq_file *m, void *v)
 85{
 86}
 87
 88static 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 */
 98static int fscache_histogram_open(struct inode *inode, struct file *file)
 99{
100	return seq_open(file, &fscache_histogram_ops);
101}
102
103const 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};