find_bit_benchmark.c (4579B)
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 29static DECLARE_BITMAP(bitmap, BITMAP_LEN) __initdata; 30static 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 */ 36static 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 52static 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 71static 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 85static 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 99static 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 118static int __init test_find_next_and_bit(const void *bitmap, 119 const void *bitmap2, unsigned long len) 120{ 121 unsigned long i, cnt; 122 ktime_t time; 123 124 time = ktime_get(); 125 for (cnt = i = 0; i < BITMAP_LEN; cnt++) 126 i = find_next_and_bit(bitmap, bitmap2, BITMAP_LEN, i + 1); 127 time = ktime_get() - time; 128 pr_err("find_next_and_bit: %18llu ns, %6ld iterations\n", time, cnt); 129 130 return 0; 131} 132 133static int __init find_bit_test(void) 134{ 135 unsigned long nbits = BITMAP_LEN / SPARSE; 136 137 pr_err("\nStart testing find_bit() with random-filled bitmap\n"); 138 139 get_random_bytes(bitmap, sizeof(bitmap)); 140 get_random_bytes(bitmap2, sizeof(bitmap2)); 141 142 test_find_next_bit(bitmap, BITMAP_LEN); 143 test_find_next_zero_bit(bitmap, BITMAP_LEN); 144 test_find_last_bit(bitmap, BITMAP_LEN); 145 146 /* 147 * test_find_first_bit() may take some time, so 148 * traverse only part of bitmap to avoid soft lockup. 149 */ 150 test_find_first_bit(bitmap, BITMAP_LEN / 10); 151 test_find_first_and_bit(bitmap, bitmap2, BITMAP_LEN / 2); 152 test_find_next_and_bit(bitmap, bitmap2, BITMAP_LEN); 153 154 pr_err("\nStart testing find_bit() with sparse bitmap\n"); 155 156 bitmap_zero(bitmap, BITMAP_LEN); 157 bitmap_zero(bitmap2, BITMAP_LEN); 158 159 while (nbits--) { 160 __set_bit(prandom_u32() % BITMAP_LEN, bitmap); 161 __set_bit(prandom_u32() % BITMAP_LEN, bitmap2); 162 } 163 164 test_find_next_bit(bitmap, BITMAP_LEN); 165 test_find_next_zero_bit(bitmap, BITMAP_LEN); 166 test_find_last_bit(bitmap, BITMAP_LEN); 167 test_find_first_bit(bitmap, BITMAP_LEN); 168 test_find_first_and_bit(bitmap, bitmap2, BITMAP_LEN); 169 test_find_next_and_bit(bitmap, bitmap2, BITMAP_LEN); 170 171 /* 172 * Everything is OK. Return error just to let user run benchmark 173 * again without annoying rmmod. 174 */ 175 return -EINVAL; 176} 177module_init(find_bit_test); 178 179MODULE_LICENSE("GPL");