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_first_and_bit(void * bitmap,const void * bitmap2,unsigned long len)52 static 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
test_find_next_bit(const void * bitmap,unsigned long len)71 static 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
test_find_next_zero_bit(const void * bitmap,unsigned long len)85 static 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
test_find_last_bit(const void * bitmap,unsigned long len)99 static 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
test_find_nth_bit(const unsigned long * bitmap,unsigned long len)118 static 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
test_find_next_and_bit(const void * bitmap,const void * bitmap2,unsigned long len)134 static 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
find_bit_test(void)149 static 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(prandom_u32_max(BITMAP_LEN), bitmap);
178 __set_bit(prandom_u32_max(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 }
195 module_init(find_bit_test);
196
197 MODULE_LICENSE("GPL");
198
