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4ba281d5bd
test_find_first_bit() is intentionally sub-optimal, and may cause soft
lockup due to long time of run on some systems. So decrease length of
bitmap to traverse to avoid lockup.
With the change below, time of test execution doesn't exceed 0.2 seconds
on my testing system.
Link: http://lkml.kernel.org/r/20180420171949.15710-1-ynorov@caviumnetworks.com
Fixes: 4441fca0a2
("lib: test module for find_*_bit() functions")
Signed-off-by: Yury Norov <ynorov@caviumnetworks.com>
Reviewed-by: Andrew Morton <akpm@linux-foundation.org>
Reported-by: Fengguang Wu <fengguang.wu@intel.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
168 lines
4.3 KiB
C
168 lines
4.3 KiB
C
/*
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* Test for find_*_bit functions.
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*
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* Copyright (c) 2017 Cavium.
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*
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* This program is free software; you can redistribute it and/or
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* modify it under the terms of version 2 of the GNU General Public
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* License as published by the Free Software Foundation.
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*
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* This program is distributed in the hope that it will be useful, but
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* WITHOUT ANY WARRANTY; without even the implied warranty of
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* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
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* General Public License for more details.
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*/
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/*
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* find_bit functions are widely used in kernel, so the successful boot
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* is good enough test for correctness.
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*
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* This test is focused on performance of traversing bitmaps. Two typical
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* scenarios are reproduced:
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* - randomly filled bitmap with approximately equal number of set and
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* cleared bits;
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* - sparse bitmap with few set bits at random positions.
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*/
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#include <linux/bitops.h>
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#include <linux/kernel.h>
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#include <linux/list.h>
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#include <linux/module.h>
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#include <linux/printk.h>
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#include <linux/random.h>
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#define BITMAP_LEN (4096UL * 8 * 10)
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#define SPARSE 500
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static DECLARE_BITMAP(bitmap, BITMAP_LEN) __initdata;
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static DECLARE_BITMAP(bitmap2, BITMAP_LEN) __initdata;
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/*
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* This is Schlemiel the Painter's algorithm. It should be called after
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* all other tests for the same bitmap because it sets all bits of bitmap to 1.
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*/
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static int __init test_find_first_bit(void *bitmap, unsigned long len)
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{
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unsigned long i, cnt;
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ktime_t time;
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time = ktime_get();
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for (cnt = i = 0; i < len; cnt++) {
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i = find_first_bit(bitmap, len);
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__clear_bit(i, bitmap);
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}
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time = ktime_get() - time;
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pr_err("find_first_bit: %18llu ns, %6ld iterations\n", time, cnt);
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return 0;
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}
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static int __init test_find_next_bit(const void *bitmap, unsigned long len)
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{
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unsigned long i, cnt;
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ktime_t time;
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time = ktime_get();
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for (cnt = i = 0; i < BITMAP_LEN; cnt++)
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i = find_next_bit(bitmap, BITMAP_LEN, i) + 1;
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time = ktime_get() - time;
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pr_err("find_next_bit: %18llu ns, %6ld iterations\n", time, cnt);
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return 0;
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}
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static int __init test_find_next_zero_bit(const void *bitmap, unsigned long len)
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{
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unsigned long i, cnt;
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ktime_t time;
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time = ktime_get();
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for (cnt = i = 0; i < BITMAP_LEN; cnt++)
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i = find_next_zero_bit(bitmap, len, i) + 1;
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time = ktime_get() - time;
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pr_err("find_next_zero_bit: %18llu ns, %6ld iterations\n", time, cnt);
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return 0;
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}
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static int __init test_find_last_bit(const void *bitmap, unsigned long len)
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{
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unsigned long l, cnt = 0;
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ktime_t time;
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time = ktime_get();
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do {
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cnt++;
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l = find_last_bit(bitmap, len);
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if (l >= len)
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break;
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len = l;
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} while (len);
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time = ktime_get() - time;
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pr_err("find_last_bit: %18llu ns, %6ld iterations\n", time, cnt);
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return 0;
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}
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static int __init test_find_next_and_bit(const void *bitmap,
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const void *bitmap2, unsigned long len)
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{
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unsigned long i, cnt;
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cycles_t cycles;
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cycles = get_cycles();
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for (cnt = i = 0; i < BITMAP_LEN; cnt++)
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i = find_next_and_bit(bitmap, bitmap2, BITMAP_LEN, i+1);
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cycles = get_cycles() - cycles;
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pr_err("find_next_and_bit:\t\t%llu cycles, %ld iterations\n",
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(u64)cycles, cnt);
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return 0;
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}
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static int __init find_bit_test(void)
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{
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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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get_random_bytes(bitmap2, sizeof(bitmap2));
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test_find_next_bit(bitmap, BITMAP_LEN);
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test_find_next_zero_bit(bitmap, BITMAP_LEN);
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test_find_last_bit(bitmap, BITMAP_LEN);
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/*
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* test_find_first_bit() may take some time, so
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* traverse only part of bitmap to avoid soft lockup.
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*/
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test_find_first_bit(bitmap, BITMAP_LEN / 10);
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test_find_next_and_bit(bitmap, bitmap2, 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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bitmap_zero(bitmap2, BITMAP_LEN);
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while (nbits--) {
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__set_bit(prandom_u32() % BITMAP_LEN, bitmap);
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__set_bit(prandom_u32() % BITMAP_LEN, bitmap2);
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}
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test_find_next_bit(bitmap, BITMAP_LEN);
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test_find_next_zero_bit(bitmap, BITMAP_LEN);
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test_find_last_bit(bitmap, BITMAP_LEN);
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test_find_first_bit(bitmap, BITMAP_LEN);
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test_find_next_and_bit(bitmap, bitmap2, BITMAP_LEN);
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/*
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* Everything is OK. Return error just to let user run benchmark
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* again without annoying rmmod.
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*/
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return -EINVAL;
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}
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module_init(find_bit_test);
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MODULE_LICENSE("GPL");
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