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Commit 4441fca0 authored by Yury Norov's avatar Yury Norov Committed by Linus Torvalds
Browse files

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

[arnd@arndb.de: use correct format string for find-bit tests]
  Link: http://lkml.kernel.org/r/20171113135605.3166307-1-arnd@arndb.de
Link: http://lkml.kernel.org/r/20171109140714.13168-1-ynorov@caviumnetworks.com


Signed-off-by: default avatarYury Norov <ynorov@caviumnetworks.com>
Signed-off-by: default avatarArnd Bergmann <arnd@arndb.de>
Reviewed-by: default avatarClement Courbet <courbet@google.com>
Cc: Alexey Dobriyan <adobriyan@gmail.com>
Cc: Matthew Wilcox <mawilcox@microsoft.com>
Cc: Rasmus Villemoes <linux@rasmusvillemoes.dk>
Signed-off-by: default avatarAndrew Morton <akpm@linux-foundation.org>
Signed-off-by: default avatarLinus Torvalds <torvalds@linux-foundation.org>
parent 0b548e33

lib/Kconfig.debug

+9 −0
Original line number Diff line number Diff line
@@ -1850,6 +1850,15 @@ config TEST_BPF 


	  If unsure, say N.



config TEST_FIND_BIT

	tristate "Test find_bit functions"

	default n

	help

	  This builds the "test_find_bit" module that measure find_*_bit()

	  functions performance.



	  If unsure, say N.



config TEST_FIRMWARE

	tristate "Test firmware loading via userspace interface"

	default n

lib/Makefile

+1 −0
Original line number Diff line number Diff line
@@ -47,6 +47,7 @@ obj-y += hexdump.o 
obj-$(CONFIG_TEST_HEXDUMP) += test_hexdump.o

obj-y += kstrtox.o

obj-$(CONFIG_TEST_BPF) += test_bpf.o

obj-$(CONFIG_TEST_FIND_BIT) += test_find_bit.o

obj-$(CONFIG_TEST_FIRMWARE) += test_firmware.o

obj-$(CONFIG_TEST_SYSCTL) += test_sysctl.o

obj-$(CONFIG_TEST_HASH) += test_hash.o test_siphash.o

lib/test_find_bit.c

0 → 100644
+144 −0
Original line number Diff line number Diff line 
/*

 * 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;



/*

 * 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;



	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);



	return 0;

}



static int __init test_find_next_bit(const void *bitmap, unsigned long len)

{

	unsigned long i, cnt;

	cycles_t cycles;



	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);



	return 0;

}



static int __init test_find_next_zero_bit(const void *bitmap, unsigned long len)

{

	unsigned long i, cnt;

	cycles_t cycles;



	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);



	return 0;

}



static int __init test_find_last_bit(const void *bitmap, unsigned long len)

{

	unsigned long l, cnt = 0;

	cycles_t cycles;



	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);



	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));



	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);



	pr_err("\nStart testing find_bit() with sparse bitmap\n");



	bitmap_zero(bitmap, BITMAP_LEN);



	while (nbits--)

		__set_bit(prandom_u32() % BITMAP_LEN, bitmap);



	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);



	return 0;

}

module_init(find_bit_test);



static void __exit test_find_bit_cleanup(void)

{

}

module_exit(test_find_bit_cleanup);



MODULE_LICENSE("GPL");