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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 
29 static DECLARE_BITMAP(bitmap, BITMAP_LEN) __initdata;
30 static 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  */
test_find_first_bit(void * bitmap,unsigned long len)36 static 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 
test_find_next_bit(const void * bitmap,unsigned long len)52 static 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 
test_find_next_zero_bit(const void * bitmap,unsigned long len)66 static 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 
test_find_last_bit(const void * bitmap,unsigned long len)80 static 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 
test_find_next_and_bit(const void * bitmap,const void * bitmap2,unsigned long len)99 static 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 
find_bit_test(void)114 static 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 }
156 module_init(find_bit_test);
157 
158 MODULE_LICENSE("GPL");
159