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_next_bit(const void *bitmap, unsigned long len)
53{
54	unsigned long i, cnt;
55	ktime_t time;
56
57	time = ktime_get();
58	for (cnt = i = 0; i < BITMAP_LEN; cnt++)
59		i = find_next_bit(bitmap, BITMAP_LEN, i) + 1;
60	time = ktime_get() - time;
61	pr_err("find_next_bit:      %18llu ns, %6ld iterations\n", time, cnt);
62
63	return 0;
64}
65
66static int __init test_find_next_zero_bit(const void *bitmap, unsigned long len)
67{
68	unsigned long i, cnt;
69	ktime_t time;
70
71	time = ktime_get();
72	for (cnt = i = 0; i < BITMAP_LEN; cnt++)
73		i = find_next_zero_bit(bitmap, len, i) + 1;
74	time = ktime_get() - time;
75	pr_err("find_next_zero_bit: %18llu ns, %6ld iterations\n", time, cnt);
76
77	return 0;
78}
79
80static int __init test_find_last_bit(const void *bitmap, unsigned long len)
81{
82	unsigned long l, cnt = 0;
83	ktime_t time;
84
85	time = ktime_get();
86	do {
87		cnt++;
88		l = find_last_bit(bitmap, len);
89		if (l >= len)
90			break;
91		len = l;
92	} while (len);
93	time = ktime_get() - time;
94	pr_err("find_last_bit:      %18llu ns, %6ld iterations\n", time, cnt);
95
96	return 0;
97}
98
99static int __init test_find_next_and_bit(const void *bitmap,
100		const void *bitmap2, unsigned long len)
101{
102	unsigned long i, cnt;
103	ktime_t time;
104
105	time = ktime_get();
106	for (cnt = i = 0; i < BITMAP_LEN; cnt++)
107		i = find_next_and_bit(bitmap, bitmap2, BITMAP_LEN, i + 1);
108	time = ktime_get() - time;
109	pr_err("find_next_and_bit:  %18llu ns, %6ld iterations\n", time, cnt);
110
111	return 0;
112}
113
114static int __init find_bit_test(void)
115{
116	unsigned long nbits = BITMAP_LEN / SPARSE;
117
118	pr_err("\nStart testing find_bit() with random-filled bitmap\n");
119
120	get_random_bytes(bitmap, sizeof(bitmap));
121	get_random_bytes(bitmap2, sizeof(bitmap2));
122
123	test_find_next_bit(bitmap, BITMAP_LEN);
124	test_find_next_zero_bit(bitmap, BITMAP_LEN);
125	test_find_last_bit(bitmap, BITMAP_LEN);
126
127	/*
128	 * test_find_first_bit() may take some time, so
129	 * traverse only part of bitmap to avoid soft lockup.
130	 */
131	test_find_first_bit(bitmap, BITMAP_LEN / 10);
132	test_find_next_and_bit(bitmap, bitmap2, BITMAP_LEN);
133
134	pr_err("\nStart testing find_bit() with sparse bitmap\n");
135
136	bitmap_zero(bitmap, BITMAP_LEN);
137	bitmap_zero(bitmap2, BITMAP_LEN);
138
139	while (nbits--) {
140		__set_bit(prandom_u32() % BITMAP_LEN, bitmap);
141		__set_bit(prandom_u32() % BITMAP_LEN, bitmap2);
142	}
143
144	test_find_next_bit(bitmap, BITMAP_LEN);
145	test_find_next_zero_bit(bitmap, BITMAP_LEN);
146	test_find_last_bit(bitmap, BITMAP_LEN);
147	test_find_first_bit(bitmap, BITMAP_LEN);
148	test_find_next_and_bit(bitmap, bitmap2, BITMAP_LEN);
149
150	/*
151	 * Everything is OK. Return error just to let user run benchmark
152	 * again without annoying rmmod.
153	 */
154	return -EINVAL;
155}
156module_init(find_bit_test);
157
158MODULE_LICENSE("GPL");
159