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lib: test module for find_*_bit() functions
find_bit functions are widely used in the kernel, including hot paths. This module tests performance of those functions in 2 typical scenarios: randomly filled bitmap with relatively equal distribution of set and cleared bits, and sparse bitmap which has 1 set bit for 500 cleared bits. On ThunderX machine: Start testing find_bit() with random-filled bitmap find_next_bit: 240043 cycles, 164062 iterations find_next_zero_bit: 312848 cycles, 163619 iterations find_last_bit: 193748 cycles, 164062 iterations find_first_bit: 177720874 cycles, 164062 iterations Start testing find_bit() with sparse bitmap find_next_bit: 3633 cycles, 656 iterations find_next_zero_bit: 620399 cycles, 327025 iterations find_last_bit: 3038 cycles, 656 iterations find_first_bit: 691407 cycles, 656 iterations [[email protected]: use correct format string for find-bit tests] Link: http://lkml.kernel.org/r/[email protected] Link: http://lkml.kernel.org/r/[email protected] Signed-off-by: Yury Norov <[email protected]> Signed-off-by: Arnd Bergmann <[email protected]> Reviewed-by: Clement Courbet <[email protected]> Cc: Alexey Dobriyan <[email protected]> Cc: Matthew Wilcox <[email protected]> Cc: Rasmus Villemoes <[email protected]> Signed-off-by: Andrew Morton <[email protected]> Signed-off-by: Linus Torvalds <[email protected]>
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/* | ||
* 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. | ||
*/ | ||
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/* | ||
* 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. | ||
*/ | ||
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#include <linux/bitops.h> | ||
#include <linux/kernel.h> | ||
#include <linux/list.h> | ||
#include <linux/module.h> | ||
#include <linux/printk.h> | ||
#include <linux/random.h> | ||
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#define BITMAP_LEN (4096UL * 8 * 10) | ||
#define SPARSE 500 | ||
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static DECLARE_BITMAP(bitmap, BITMAP_LEN) __initdata; | ||
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/* | ||
* 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; | ||
cycles_t cycles; | ||
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cycles = get_cycles(); | ||
for (cnt = i = 0; i < len; cnt++) { | ||
i = find_first_bit(bitmap, len); | ||
__clear_bit(i, bitmap); | ||
} | ||
cycles = get_cycles() - cycles; | ||
pr_err("find_first_bit:\t\t%llu cycles,\t%ld iterations\n", | ||
(u64)cycles, cnt); | ||
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return 0; | ||
} | ||
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static int __init test_find_next_bit(const void *bitmap, unsigned long len) | ||
{ | ||
unsigned long i, cnt; | ||
cycles_t cycles; | ||
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cycles = get_cycles(); | ||
for (cnt = i = 0; i < BITMAP_LEN; cnt++) | ||
i = find_next_bit(bitmap, BITMAP_LEN, i) + 1; | ||
cycles = get_cycles() - cycles; | ||
pr_err("find_next_bit:\t\t%llu cycles,\t%ld iterations\n", | ||
(u64)cycles, cnt); | ||
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return 0; | ||
} | ||
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static int __init test_find_next_zero_bit(const void *bitmap, unsigned long len) | ||
{ | ||
unsigned long i, cnt; | ||
cycles_t cycles; | ||
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cycles = get_cycles(); | ||
for (cnt = i = 0; i < BITMAP_LEN; cnt++) | ||
i = find_next_zero_bit(bitmap, len, i) + 1; | ||
cycles = get_cycles() - cycles; | ||
pr_err("find_next_zero_bit:\t%llu cycles,\t%ld iterations\n", | ||
(u64)cycles, cnt); | ||
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return 0; | ||
} | ||
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static int __init test_find_last_bit(const void *bitmap, unsigned long len) | ||
{ | ||
unsigned long l, cnt = 0; | ||
cycles_t cycles; | ||
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cycles = get_cycles(); | ||
do { | ||
cnt++; | ||
l = find_last_bit(bitmap, len); | ||
if (l >= len) | ||
break; | ||
len = l; | ||
} while (len); | ||
cycles = get_cycles() - cycles; | ||
pr_err("find_last_bit:\t\t%llu cycles,\t%ld iterations\n", | ||
(u64)cycles, cnt); | ||
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return 0; | ||
} | ||
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static int __init find_bit_test(void) | ||
{ | ||
unsigned long nbits = BITMAP_LEN / SPARSE; | ||
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pr_err("\nStart testing find_bit() with random-filled bitmap\n"); | ||
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get_random_bytes(bitmap, sizeof(bitmap)); | ||
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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); | ||
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pr_err("\nStart testing find_bit() with sparse bitmap\n"); | ||
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bitmap_zero(bitmap, BITMAP_LEN); | ||
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while (nbits--) | ||
__set_bit(prandom_u32() % BITMAP_LEN, bitmap); | ||
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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); | ||
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return 0; | ||
} | ||
module_init(find_bit_test); | ||
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static void __exit test_find_bit_cleanup(void) | ||
{ | ||
} | ||
module_exit(test_find_bit_cleanup); | ||
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MODULE_LICENSE("GPL"); |