1// SPDX-License-Identifier: GPL-2.0-only
2/*
3 * Test for find_*_bit functions.
4 *
5 * Copyright (c) 2017 Cavium.
6 */
7
8/*
9 * find_bit functions are widely used in kernel, so the successful boot
10 * is good enough test for correctness.
11 *
12 * This test is focused on performance of traversing bitmaps. Two typical
13 * scenarios are reproduced:
14 * - randomly filled bitmap with approximately equal number of set and
15 *   cleared bits;
16 * - sparse bitmap with few set bits at random positions.
17 */
18
19#include <linux/bitops.h>
20#include <linux/kernel.h>
21#include <linux/list.h>
22#include <linux/module.h>
23#include <linux/printk.h>
24#include <linux/random.h>
25
26#define BITMAP_LEN	(4096UL * 8 * 10)
27#define SPARSE		500
28
29static DECLARE_BITMAP(bitmap, BITMAP_LEN) __initdata;
30static DECLARE_BITMAP(bitmap2, BITMAP_LEN) __initdata;
31
32/*
33 * This is Schlemiel the Painter's algorithm. It should be called after
34 * all other tests for the same bitmap because it sets all bits of bitmap to 1.
35 */
36static int __init test_find_first_bit(void *bitmap, unsigned long len)
37{
38	unsigned long i, cnt;
39	ktime_t time;
40
41	time = ktime_get();
42	for (cnt = i = 0; i < len; cnt++) {
43		i = find_first_bit(bitmap, len);
44		__clear_bit(i, bitmap);
45	}
46	time = ktime_get() - time;
47	pr_err("find_first_bit:     %18llu ns, %6ld iterations\n", time, cnt);
48
49	return 0;
50}
51
52static int __init test_find_first_and_bit(void *bitmap, const void *bitmap2, unsigned long len)
53{
54	static DECLARE_BITMAP(cp, BITMAP_LEN) __initdata;
55	unsigned long i, cnt;
56	ktime_t time;
57
58	bitmap_copy(cp, bitmap, BITMAP_LEN);
59
60	time = ktime_get();
61	for (cnt = i = 0; i < len; cnt++) {
62		i = find_first_and_bit(cp, bitmap2, len);
63		__clear_bit(i, cp);
64	}
65	time = ktime_get() - time;
66	pr_err("find_first_and_bit: %18llu ns, %6ld iterations\n", time, cnt);
67
68	return 0;
69}
70
71static int __init test_find_next_bit(const void *bitmap, unsigned long len)
72{
73	unsigned long i, cnt;
74	ktime_t time;
75
76	time = ktime_get();
77	for (cnt = i = 0; i < BITMAP_LEN; cnt++)
78		i = find_next_bit(bitmap, BITMAP_LEN, i) + 1;
79	time = ktime_get() - time;
80	pr_err("find_next_bit:      %18llu ns, %6ld iterations\n", time, cnt);
81
82	return 0;
83}
84
85static int __init test_find_next_zero_bit(const void *bitmap, unsigned long len)
86{
87	unsigned long i, cnt;
88	ktime_t time;
89
90	time = ktime_get();
91	for (cnt = i = 0; i < BITMAP_LEN; cnt++)
92		i = find_next_zero_bit(bitmap, len, i) + 1;
93	time = ktime_get() - time;
94	pr_err("find_next_zero_bit: %18llu ns, %6ld iterations\n", time, cnt);
95
96	return 0;
97}
98
99static int __init test_find_last_bit(const void *bitmap, unsigned long len)
100{
101	unsigned long l, cnt = 0;
102	ktime_t time;
103
104	time = ktime_get();
105	do {
106		cnt++;
107		l = find_last_bit(bitmap, len);
108		if (l >= len)
109			break;
110		len = l;
111	} while (len);
112	time = ktime_get() - time;
113	pr_err("find_last_bit:      %18llu ns, %6ld iterations\n", time, cnt);
114
115	return 0;
116}
117
118static int __init test_find_nth_bit(const unsigned long *bitmap, unsigned long len)
119{
120	unsigned long l, n, w = bitmap_weight(bitmap, len);
121	ktime_t time;
122
123	time = ktime_get();
124	for (n = 0; n < w; n++) {
125		l = find_nth_bit(bitmap, len, n);
126		WARN_ON(l >= len);
127	}
128	time = ktime_get() - time;
129	pr_err("find_nth_bit:       %18llu ns, %6ld iterations\n", time, w);
130
131	return 0;
132}
133
134static int __init test_find_next_and_bit(const void *bitmap,
135		const void *bitmap2, unsigned long len)
136{
137	unsigned long i, cnt;
138	ktime_t time;
139
140	time = ktime_get();
141	for (cnt = i = 0; i < BITMAP_LEN; cnt++)
142		i = find_next_and_bit(bitmap, bitmap2, BITMAP_LEN, i + 1);
143	time = ktime_get() - time;
144	pr_err("find_next_and_bit:  %18llu ns, %6ld iterations\n", time, cnt);
145
146	return 0;
147}
148
149static int __init find_bit_test(void)
150{
151	unsigned long nbits = BITMAP_LEN / SPARSE;
152
153	pr_err("\nStart testing find_bit() with random-filled bitmap\n");
154
155	get_random_bytes(bitmap, sizeof(bitmap));
156	get_random_bytes(bitmap2, sizeof(bitmap2));
157
158	test_find_next_bit(bitmap, BITMAP_LEN);
159	test_find_next_zero_bit(bitmap, BITMAP_LEN);
160	test_find_last_bit(bitmap, BITMAP_LEN);
161	test_find_nth_bit(bitmap, BITMAP_LEN / 10);
162
163	/*
164	 * test_find_first_bit() may take some time, so
165	 * traverse only part of bitmap to avoid soft lockup.
166	 */
167	test_find_first_bit(bitmap, BITMAP_LEN / 10);
168	test_find_first_and_bit(bitmap, bitmap2, BITMAP_LEN / 2);
169	test_find_next_and_bit(bitmap, bitmap2, BITMAP_LEN);
170
171	pr_err("\nStart testing find_bit() with sparse bitmap\n");
172
173	bitmap_zero(bitmap, BITMAP_LEN);
174	bitmap_zero(bitmap2, BITMAP_LEN);
175
176	while (nbits--) {
177		__set_bit(get_random_u32_below(BITMAP_LEN), bitmap);
178		__set_bit(get_random_u32_below(BITMAP_LEN), bitmap2);
179	}
180
181	test_find_next_bit(bitmap, BITMAP_LEN);
182	test_find_next_zero_bit(bitmap, BITMAP_LEN);
183	test_find_last_bit(bitmap, BITMAP_LEN);
184	test_find_nth_bit(bitmap, BITMAP_LEN);
185	test_find_first_bit(bitmap, BITMAP_LEN);
186	test_find_first_and_bit(bitmap, bitmap2, BITMAP_LEN);
187	test_find_next_and_bit(bitmap, bitmap2, BITMAP_LEN);
188
189	/*
190	 * Everything is OK. Return error just to let user run benchmark
191	 * again without annoying rmmod.
192	 */
193	return -EINVAL;
194}
195module_init(find_bit_test);
196
197MODULE_LICENSE("GPL");
198