histogram.c

Go to the documentation of this file.

/* FS-Cache latency histogram
 *
 * Copyright (C) 2008 Red Hat, Inc. All Rights Reserved.
 * Written by David Howells ([email protected])
 *
 * This program is free software; you can redistribute it and/or
 * modify it under the terms of the GNU General Public Licence
 * as published by the Free Software Foundation; either version
 * 2 of the Licence, or (at your option) any later version.
 */

#define FSCACHE_DEBUG_LEVEL THREAD
#include <linux/module.h>
#include <linux/proc_fs.h>
#include <linux/seq_file.h>
#include "internal.h"

atomic_t fscache_obj_instantiate_histogram[HZ];
atomic_t fscache_objs_histogram[HZ];
atomic_t fscache_ops_histogram[HZ];
atomic_t fscache_retrieval_delay_histogram[HZ];
atomic_t fscache_retrieval_histogram[HZ];

/*
 * display the time-taken histogram
 */
static int fscache_histogram_show(struct seq_file *m, void *v)
{
    unsigned long index;
    unsigned n[5], t;

    switch ((unsigned long) v) {
    case 1:
        seq_puts(m, "JIFS  SECS  OBJ INST  OP RUNS   OBJ RUNS "
             " RETRV DLY RETRIEVLS\n");
        return 0;
    case 2:
        seq_puts(m, "===== ===== ========= ========= ========="
             " ========= =========\n");
        return 0;
    default:
        index = (unsigned long) v - 3;
        n[0] = atomic_read(&fscache_obj_instantiate_histogram[index]);
        n[1] = atomic_read(&fscache_ops_histogram[index]);
        n[2] = atomic_read(&fscache_objs_histogram[index]);
        n[3] = atomic_read(&fscache_retrieval_delay_histogram[index]);
        n[4] = atomic_read(&fscache_retrieval_histogram[index]);
        if (!(n[0] | n[1] | n[2] | n[3] | n[4]))
            return 0;

        t = (index * 1000) / HZ;

        seq_printf(m, "%4lu  0.%03u %9u %9u %9u %9u %9u\n",
               index, t, n[0], n[1], n[2], n[3], n[4]);
        return 0;
    }
}

/*
 * set up the iterator to start reading from the first line
 */
static void *fscache_histogram_start(struct seq_file *m, loff_t *_pos)
{
    if ((unsigned long long)*_pos >= HZ + 2)
        return NULL;
    if (*_pos == 0)
        *_pos = 1;
    return (void *)(unsigned long) *_pos;
}

/*
 * move to the next line
 */
static void *fscache_histogram_next(struct seq_file *m, void *v, loff_t *pos)
{
    (*pos)++;
    return (unsigned long long)*pos > HZ + 2 ?
        NULL : (void *)(unsigned long) *pos;
}

/*
 * clean up after reading
 */
static void fscache_histogram_stop(struct seq_file *m, void *v)
{
}

static const struct seq_operations fscache_histogram_ops = {
    .start      = fscache_histogram_start,
    .stop       = fscache_histogram_stop,
    .next       = fscache_histogram_next,
    .show       = fscache_histogram_show,
};

/*
 * open "/proc/fs/fscache/histogram" to provide latency data
 */
static int fscache_histogram_open(struct inode *inode, struct file *file)
{
    return seq_open(file, &fscache_histogram_ops);
}

const struct file_operations fscache_histogram_fops = {
    .owner      = THIS_MODULE,
    .open       = fscache_histogram_open,
    .read       = seq_read,
    .llseek     = seq_lseek,
    .release    = seq_release,
};