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Diffstat (limited to 'lib/find_bit_benchmark.c')
| -rw-r--r-- | lib/find_bit_benchmark.c | 162 |
1 files changed, 162 insertions, 0 deletions
diff --git a/lib/find_bit_benchmark.c b/lib/find_bit_benchmark.c new file mode 100644 index 000000000000..5985a25e6cbc --- /dev/null +++ b/lib/find_bit_benchmark.c @@ -0,0 +1,162 @@ +/* + * Test for find_*_bit functions. + * + * Copyright (c) 2017 Cavium. + * + * This program is free software; you can redistribute it and/or + * modify it under the terms of version 2 of the GNU General Public + * License as published by the Free Software Foundation. + * + * This program is distributed in the hope that it will be useful, but + * WITHOUT ANY WARRANTY; without even the implied warranty of + * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU + * General Public License for more details. + */ + +/* + * find_bit functions are widely used in kernel, so the successful boot + * is good enough test for correctness. + * + * This test is focused on performance of traversing bitmaps. Two typical + * scenarios are reproduced: + * - randomly filled bitmap with approximately equal number of set and + * cleared bits; + * - sparse bitmap with few set bits at random positions. + */ + +#include <linux/bitops.h> +#include <linux/kernel.h> +#include <linux/list.h> +#include <linux/module.h> +#include <linux/printk.h> +#include <linux/random.h> + +#define BITMAP_LEN (4096UL * 8 * 10) +#define SPARSE 500 + +static DECLARE_BITMAP(bitmap, BITMAP_LEN) __initdata; +static DECLARE_BITMAP(bitmap2, BITMAP_LEN) __initdata; + +/* + * This is Schlemiel the Painter's algorithm. It should be called after + * all other tests for the same bitmap because it sets all bits of bitmap to 1. + */ +static int __init test_find_first_bit(void *bitmap, unsigned long len) +{ + unsigned long i, cnt; + ktime_t time; + + time = ktime_get(); + for (cnt = i = 0; i < len; cnt++) { + i = find_first_bit(bitmap, len); + __clear_bit(i, bitmap); + } + time = ktime_get() - time; + pr_err("find_first_bit: %18llu ns, %6ld iterations\n", time, cnt); + + return 0; +} + +static int __init test_find_next_bit(const void *bitmap, unsigned long len) +{ + unsigned long i, cnt; + ktime_t time; + + time = ktime_get(); + for (cnt = i = 0; i < BITMAP_LEN; cnt++) + i = find_next_bit(bitmap, BITMAP_LEN, i) + 1; + time = ktime_get() - time; + pr_err("find_next_bit: %18llu ns, %6ld iterations\n", time, cnt); + + return 0; +} + +static int __init test_find_next_zero_bit(const void *bitmap, unsigned long len) +{ + unsigned long i, cnt; + ktime_t time; + + time = ktime_get(); + for (cnt = i = 0; i < BITMAP_LEN; cnt++) + i = find_next_zero_bit(bitmap, len, i) + 1; + time = ktime_get() - time; + pr_err("find_next_zero_bit: %18llu ns, %6ld iterations\n", time, cnt); + + return 0; +} + +static int __init test_find_last_bit(const void *bitmap, unsigned long len) +{ + unsigned long l, cnt = 0; + ktime_t time; + + time = ktime_get(); + do { + cnt++; + l = find_last_bit(bitmap, len); + if (l >= len) + break; + len = l; + } while (len); + time = ktime_get() - time; + pr_err("find_last_bit: %18llu ns, %6ld iterations\n", time, cnt); + + return 0; +} + +static int __init test_find_next_and_bit(const void *bitmap, + const void *bitmap2, unsigned long len) +{ + unsigned long i, cnt; + cycles_t cycles; + + cycles = get_cycles(); + for (cnt = i = 0; i < BITMAP_LEN; cnt++) + i = find_next_and_bit(bitmap, bitmap2, BITMAP_LEN, i+1); + cycles = get_cycles() - cycles; + pr_err("find_next_and_bit:\t\t%llu cycles, %ld iterations\n", + (u64)cycles, cnt); + + return 0; +} + +static int __init find_bit_test(void) +{ + unsigned long nbits = BITMAP_LEN / SPARSE; + + pr_err("\nStart testing find_bit() with random-filled bitmap\n"); + + get_random_bytes(bitmap, sizeof(bitmap)); + get_random_bytes(bitmap2, sizeof(bitmap2)); + + test_find_next_bit(bitmap, BITMAP_LEN); + test_find_next_zero_bit(bitmap, BITMAP_LEN); + test_find_last_bit(bitmap, BITMAP_LEN); + test_find_first_bit(bitmap, BITMAP_LEN); + test_find_next_and_bit(bitmap, bitmap2, BITMAP_LEN); + + pr_err("\nStart testing find_bit() with sparse bitmap\n"); + + bitmap_zero(bitmap, BITMAP_LEN); + bitmap_zero(bitmap2, BITMAP_LEN); + + while (nbits--) { + __set_bit(prandom_u32() % BITMAP_LEN, bitmap); + __set_bit(prandom_u32() % BITMAP_LEN, bitmap2); + } + + test_find_next_bit(bitmap, BITMAP_LEN); + test_find_next_zero_bit(bitmap, BITMAP_LEN); + test_find_last_bit(bitmap, BITMAP_LEN); + test_find_first_bit(bitmap, BITMAP_LEN); + test_find_next_and_bit(bitmap, bitmap2, BITMAP_LEN); + + /* + * Everything is OK. Return error just to let user run benchmark + * again without annoying rmmod. + */ + return -EINVAL; +} +module_init(find_bit_test); + +MODULE_LICENSE("GPL"); |