From: Andy Shevchenko <andy@kernel.org>
To: Nathan Moinvaziri <nathan@nathanm.com>
Cc: "linux-kernel@vger.kernel.org" <linux-kernel@vger.kernel.org>
Subject: Re: [PATCH] lib/string.c: Improve strcasecmp speed by not lowering if chars match
Date: Tue, 25 Oct 2022 12:03:40 +0300 [thread overview]
Message-ID: <Y1embP5sEp/NPxK0@smile.fi.intel.com> (raw)
In-Reply-To: <CAHp75Vd4Vk0v-T3kfxApGHb-H26KTHgH59DGP3Wm4qBgunDt6A@mail.gmail.com>
On Tue, Oct 25, 2022 at 11:00:36AM +0300, Andy Shevchenko wrote:
> On Tue, Oct 25, 2022 at 4:46 AM Nathan Moinvaziri <nathan@nathanm.com> wrote:
...
> > When running tests using Quick Benchmark with two matching 256 character
> > strings these changes result in anywhere between ~6-9x speed improvement.
> >
> > * We use unsigned char instead of int similar to strncasecmp.
> > * We only subtract c1 - c2 when they are not equal.
...
> You tell us that this is more preformant, but have not provided the
> numbers. Can we see those, please?
So, I have read carefully and see the reference to some QuickBenchmark I have
no idea about. What I meant here is to have numbers provided by an (open
source) tool (maybe even in-kernel test case) that anybody can test on their
machines. You also missed details about how you run, what the data set has been
used, etc.
> Note, that you basically trash CPU cache lines when characters are not
> equal, and before doing that you have a branching. I'm unsure that
> your way is more performant than the original one.
--
With Best Regards,
Andy Shevchenko
next prev parent reply other threads:[~2022-10-25 9:06 UTC|newest]
Thread overview: 11+ messages / expand[flat|nested] mbox.gz Atom feed top
2022-10-25 1:46 [PATCH] lib/string.c: Improve strcasecmp speed by not lowering if chars match Nathan Moinvaziri
2022-10-25 8:00 ` Andy Shevchenko
2022-10-25 9:03 ` Andy Shevchenko [this message]
2022-10-25 17:53 ` Nathan Moinvaziri
2022-10-25 19:19 ` Andy Shevchenko
2022-10-27 3:29 ` Nathan Moinvaziri
2022-10-27 6:31 ` Andy Shevchenko
2022-10-25 19:32 ` Christophe JAILLET
2022-10-25 23:27 ` Nathan Moinvaziri
2022-10-25 19:55 ` Rasmus Villemoes
2022-10-25 22:37 ` Nathan Moinvaziri
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