linux-imx

/*

 * Test for find_*_bit functions.

 *

 * Copyright (c) 2017 Cavium.

 *

 * This program is free software; you can redistribute it and/or

 * modify it under the terms of version 2 of the GNU General Public

 * License as published by the Free Software Foundation.

 *

 * This program is distributed in the hope that it will be useful, but

 * WITHOUT ANY WARRANTY; without even the implied warranty of

 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU

 * General Public License for more details.

 */

​

/*

 * find_bit functions are widely used in kernel, so the successful boot

 * is good enough test for correctness.

 *

 * This test is focused on performance of traversing bitmaps. Two typical

 * scenarios are reproduced:

 * - randomly filled bitmap with approximately equal number of set and

 *   cleared bits;

 * - sparse bitmap with few set bits at random positions.

 */

​

#include <linux/bitops.h>

#include <linux/kernel.h>

#include <linux/list.h>

#include <linux/module.h>

#include <linux/printk.h>

#include <linux/random.h>

​

#define BITMAP_LEN  (4096UL * 8 * 10)

#define SPARSE      500

​

static DECLARE_BITMAP(bitmap, BITMAP_LEN) __initdata;

static DECLARE_BITMAP(bitmap2, BITMAP_LEN) __initdata;

​

/*

 * This is Schlemiel the Painter's algorithm. It should be called after

 * all other tests for the same bitmap because it sets all bits of bitmap to 1.

 */

static int __init test_find_first_bit(void *bitmap, unsigned long len)

{

    unsigned long i, cnt;

    ktime_t time;

​

    time = ktime_get();

    for (cnt = i = 0; i < len; cnt++) {

        i = find_first_bit(bitmap, len);

        __clear_bit(i, bitmap);

    }

    time = ktime_get() - time;

    pr_err("find_first_bit:     %18llu ns, %6ld iterations\n", time, cnt);

​

    return 0;

}

​

static int __init test_find_next_bit(const void *bitmap, unsigned long len)

{

    unsigned long i, cnt;

    ktime_t time;