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Currently find_first_and_bit() is an alias to find_next_and_bit(). However,
it is widely used in cpumask, so it worth to optimize it. This patch adds
its own implementation for find_first_and_bit().
On x86_64 find_bit_benchmark says:
Before (#define find_first_and_bit(...) find_next_and_bit(..., 0):
Start testing find_bit() with random-filled bitmap
[ 140.291468] find_first_and_bit: 46890919 ns, 32671 iterations
Start testing find_bit() with sparse bitmap
[ 140.295028] find_first_and_bit: 7103 ns, 1 iterations
After:
Start testing find_bit() with random-filled bitmap
[ 162.574907] find_first_and_bit: 25045813 ns, 32846 iterations
Start testing find_bit() with sparse bitmap
[ 162.578458] find_first_and_bit: 4900 ns, 1 iterations
(Thanks to Alexey Klimov for thorough testing.)
Signed-off-by: Yury Norov <yury.norov@gmail.com>
Tested-by: Wolfram Sang <wsa+renesas@sang-engineering.com>
Tested-by: Alexey Klimov <aklimov@redhat.com>
Based on 1 normalized pattern(s):
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
extracted by the scancode license scanner the SPDX license identifier
GPL-2.0-only
has been chosen to replace the boilerplate/reference in 64 file(s).
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Reviewed-by: Alexios Zavras <alexios.zavras@intel.com>
Reviewed-by: Allison Randal <allison@lohutok.net>
Cc: linux-spdx@vger.kernel.org
Link: https://lkml.kernel.org/r/20190529141901.894819585@linutronix.de
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
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>
