// SPDX-License-Identifier: GPL-2.0-only/* * Test for find_*_bit functions. * * Copyright (c) 2017 Cavium. */ /* * 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; 	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\n", 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\n", 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\n", 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;	ktime_t time; 	time = ktime_get();	for (cnt = i = 0; i < BITMAP_LEN; cnt++)		i = find_next_and_bit(bitmap, bitmap2, BITMAP_LEN, i + 1);	time = ktime_get() - time;	pr_err("find_next_and_bit:  %18llu ns, %6ld iterations\n", time, cnt); 	return 0;} static int __init find_bit_test(void){	unsigned long nbits = BITMAP_LEN / SPARSE; 	pr_err("\nStart testing find_bit() with random-filled bitmap\n"); 	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("\nStart testing find_bit() with sparse bitmap\n"); 	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");