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

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: default avatarYury Norov <[email protected]>
Signed-off-by: default avatarArnd Bergmann <[email protected]>
Reviewed-by: default avatarClement Courbet <[email protected]>
Cc: Alexey Dobriyan <[email protected]>
Cc: Matthew Wilcox <[email protected]>
Cc: Rasmus Villemoes <[email protected]>
Signed-off-by: default avatarAndrew Morton <[email protected]>
Signed-off-by: default avatarLinus Torvalds <[email protected]>
parent 0b548e33
......@@ -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
......
......@@ -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
......
/*
* 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");
Markdown is supported
0% or
You are about to add 0 people to the discussion. Proceed with caution.
Finish editing this message first!
Please register or to comment