/*
   * 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
  ", time, cnt);

  
  	return 0;
  }
  
  static int __init test_find_next_bit(const void *bitmap, unsigned long len)
  {
  	unsigned long i, cnt;

  	ktime_t time;

  	time = ktime_get();

  	for (cnt = i = 0; i < BITMAP_LEN; cnt++)
  		i = find_next_bit(bitmap, BITMAP_LEN, i) + 1;

  	time = ktime_get() - time;
  	pr_err("find_next_bit:      %18llu ns, %6ld iterations
  ", time, cnt);

  
  	return 0;
  }
  
  static int __init test_find_next_zero_bit(const void *bitmap, unsigned long len)
  {
  	unsigned long i, cnt;

  	ktime_t time;

  	time = ktime_get();

  	for (cnt = i = 0; i < BITMAP_LEN; cnt++)
  		i = find_next_zero_bit(bitmap, len, i) + 1;

  	time = ktime_get() - time;
  	pr_err("find_next_zero_bit: %18llu ns, %6ld iterations
  ", time, cnt);

  
  	return 0;
  }
  
  static int __init test_find_last_bit(const void *bitmap, unsigned long len)
  {
  	unsigned long l, cnt = 0;

  	ktime_t time;

  	time = ktime_get();

  	do {
  		cnt++;
  		l = find_last_bit(bitmap, len);
  		if (l >= len)
  			break;
  		len = l;
  	} while (len);

  	time = ktime_get() - time;
  	pr_err("find_last_bit:      %18llu ns, %6ld iterations
  ", time, cnt);

  
  	return 0;
  }

  static int __init test_find_next_and_bit(const void *bitmap,
  		const void *bitmap2, unsigned long len)
  {
  	unsigned long i, cnt;
  	cycles_t cycles;
  
  	cycles = get_cycles();
  	for (cnt = i = 0; i < BITMAP_LEN; cnt++)
  		i = find_next_and_bit(bitmap, bitmap2, BITMAP_LEN, i+1);
  	cycles = get_cycles() - cycles;
  	pr_err("find_next_and_bit:\t\t%llu cycles, %ld iterations
  ",
  		(u64)cycles, cnt);
  
  	return 0;
  }

  static int __init find_bit_test(void)
  {
  	unsigned long nbits = BITMAP_LEN / SPARSE;
  
  	pr_err("
  Start testing find_bit() with random-filled bitmap
  ");
  
  	get_random_bytes(bitmap, sizeof(bitmap));

  	get_random_bytes(bitmap2, sizeof(bitmap2));

  
  	test_find_next_bit(bitmap, BITMAP_LEN);
  	test_find_next_zero_bit(bitmap, BITMAP_LEN);
  	test_find_last_bit(bitmap, BITMAP_LEN);

  
  	/*
  	 * test_find_first_bit() may take some time, so
  	 * traverse only part of bitmap to avoid soft lockup.
  	 */
  	test_find_first_bit(bitmap, BITMAP_LEN / 10);

  	test_find_next_and_bit(bitmap, bitmap2, BITMAP_LEN);

  
  	pr_err("
  Start testing find_bit() with sparse bitmap
  ");
  
  	bitmap_zero(bitmap, BITMAP_LEN);

  	bitmap_zero(bitmap2, BITMAP_LEN);

  	while (nbits--) {

  		__set_bit(prandom_u32() % BITMAP_LEN, bitmap);

  		__set_bit(prandom_u32() % BITMAP_LEN, bitmap2);
  	}

  
  	test_find_next_bit(bitmap, BITMAP_LEN);
  	test_find_next_zero_bit(bitmap, BITMAP_LEN);
  	test_find_last_bit(bitmap, BITMAP_LEN);
  	test_find_first_bit(bitmap, BITMAP_LEN);

  	test_find_next_and_bit(bitmap, bitmap2, BITMAP_LEN);

  	/*
  	 * Everything is OK. Return error just to let user run benchmark
  	 * again without annoying rmmod.
  	 */
  	return -EINVAL;

  }
  module_init(find_bit_test);

  MODULE_LICENSE("GPL");