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
