lib/find_bit_benchmark.c

   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_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
  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
  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
  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
 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
 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
 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(get_random_u32_below(BITMAP_LEN), bitmap);
 178                 __set_bit(get_random_u32_below(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_DESCRIPTION("Test for find_*_bit functions");
 198 MODULE_LICENSE("GPL");