1 /*
2 * Test for find_*_bit functions.
3 *
4 * Copyright (c) 2017 Cavium.
5 *
6 * This program is free software; you can redistribute it and/or
7 * modify it under the terms of version 2 of the GNU General Public
8 * License as published by the Free Software Foundation.
9 *
10 * This program is distributed in the hope that it will be useful, but
11 * WITHOUT ANY WARRANTY; without even the implied warranty of
12 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
13 * General Public License for more details.
14 */
15
16 /*
17 * find_bit functions are widely used in kernel, so the successful boot
18 * is good enough test for correctness.
19 *
20 * This test is focused on performance of traversing bitmaps. Two typical
21 * scenarios are reproduced:
22 * - randomly filled bitmap with approximately equal number of set and
23 * cleared bits;
24 * - sparse bitmap with few set bits at random positions.
25 */
26
27 #include <linux/bitops.h>
28 #include <linux/kernel.h>
29 #include <linux/list.h>
30 #include <linux/module.h>
31 #include <linux/printk.h>
32 #include <linux/random.h>
33
34 #define BITMAP_LEN (4096UL * 8 * 10)
35 #define SPARSE 500
36
37 static DECLARE_BITMAP(bitmap, BITMAP_LEN) __initdata;
38 static DECLARE_BITMAP(bitmap2, BITMAP_LEN) __initdata;
39
40 /*
41 * This is Schlemiel the Painter's algorithm. It should be called after
42 * all other tests for the same bitmap because it sets all bits of bitmap to 1.
43 */
test_find_first_bit(void * bitmap,unsigned long len)44 static int __init test_find_first_bit(void *bitmap, unsigned long len)
45 {
46 unsigned long i, cnt;
47 ktime_t time;
48
49 time = ktime_get();
50 for (cnt = i = 0; i < len; cnt++) {
51 i = find_first_bit(bitmap, len);
52 __clear_bit(i, bitmap);
53 }
54 time = ktime_get() - time;
55 pr_err("find_first_bit: %18llu ns, %6ld iterations\n", time, cnt);
56
57 return 0;
58 }
59
test_find_next_bit(const void * bitmap,unsigned long len)60 static int __init test_find_next_bit(const void *bitmap, unsigned long len)
61 {
62 unsigned long i, cnt;
63 ktime_t time;
64
65 time = ktime_get();
66 for (cnt = i = 0; i < BITMAP_LEN; cnt++)
67 i = find_next_bit(bitmap, BITMAP_LEN, i) + 1;
68 time = ktime_get() - time;
69 pr_err("find_next_bit: %18llu ns, %6ld iterations\n", time, cnt);
70
71 return 0;
72 }
73
test_find_next_zero_bit(const void * bitmap,unsigned long len)74 static int __init test_find_next_zero_bit(const void *bitmap, unsigned long len)
75 {
76 unsigned long i, cnt;
77 ktime_t time;
78
79 time = ktime_get();
80 for (cnt = i = 0; i < BITMAP_LEN; cnt++)
81 i = find_next_zero_bit(bitmap, len, i) + 1;
82 time = ktime_get() - time;
83 pr_err("find_next_zero_bit: %18llu ns, %6ld iterations\n", time, cnt);
84
85 return 0;
86 }
87
test_find_last_bit(const void * bitmap,unsigned long len)88 static int __init test_find_last_bit(const void *bitmap, unsigned long len)
89 {
90 unsigned long l, cnt = 0;
91 ktime_t time;
92
93 time = ktime_get();
94 do {
95 cnt++;
96 l = find_last_bit(bitmap, len);
97 if (l >= len)
98 break;
99 len = l;
100 } while (len);
101 time = ktime_get() - time;
102 pr_err("find_last_bit: %18llu ns, %6ld iterations\n", time, cnt);
103
104 return 0;
105 }
106
test_find_next_and_bit(const void * bitmap,const void * bitmap2,unsigned long len)107 static int __init test_find_next_and_bit(const void *bitmap,
108 const void *bitmap2, unsigned long len)
109 {
110 unsigned long i, cnt;
111 cycles_t cycles;
112
113 cycles = get_cycles();
114 for (cnt = i = 0; i < BITMAP_LEN; cnt++)
115 i = find_next_and_bit(bitmap, bitmap2, BITMAP_LEN, i+1);
116 cycles = get_cycles() - cycles;
117 pr_err("find_next_and_bit:\t\t%llu cycles, %ld iterations\n",
118 (u64)cycles, cnt);
119
120 return 0;
121 }
122
find_bit_test(void)123 static int __init find_bit_test(void)
124 {
125 unsigned long nbits = BITMAP_LEN / SPARSE;
126
127 pr_err("\nStart testing find_bit() with random-filled bitmap\n");
128
129 get_random_bytes(bitmap, sizeof(bitmap));
130 get_random_bytes(bitmap2, sizeof(bitmap2));
131
132 test_find_next_bit(bitmap, BITMAP_LEN);
133 test_find_next_zero_bit(bitmap, BITMAP_LEN);
134 test_find_last_bit(bitmap, BITMAP_LEN);
135
136 /*
137 * test_find_first_bit() may take some time, so
138 * traverse only part of bitmap to avoid soft lockup.
139 */
140 test_find_first_bit(bitmap, BITMAP_LEN / 10);
141 test_find_next_and_bit(bitmap, bitmap2, BITMAP_LEN);
142
143 pr_err("\nStart testing find_bit() with sparse bitmap\n");
144
145 bitmap_zero(bitmap, BITMAP_LEN);
146 bitmap_zero(bitmap2, BITMAP_LEN);
147
148 while (nbits--) {
149 __set_bit(prandom_u32() % BITMAP_LEN, bitmap);
150 __set_bit(prandom_u32() % BITMAP_LEN, bitmap2);
151 }
152
153 test_find_next_bit(bitmap, BITMAP_LEN);
154 test_find_next_zero_bit(bitmap, BITMAP_LEN);
155 test_find_last_bit(bitmap, BITMAP_LEN);
156 test_find_first_bit(bitmap, BITMAP_LEN);
157 test_find_next_and_bit(bitmap, bitmap2, BITMAP_LEN);
158
159 /*
160 * Everything is OK. Return error just to let user run benchmark
161 * again without annoying rmmod.
162 */
163 return -EINVAL;
164 }
165 module_init(find_bit_test);
166
167 MODULE_LICENSE("GPL");
168
