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 */ 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 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 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 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 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 } 113 114 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