Messages in this thread | | | From | Nathan Moinvaziri <> | Subject | RE: [PATCH] lib/string.c: Improve strcasecmp speed by not lowering if chars match | Date | Tue, 25 Oct 2022 17:53:49 +0000 |
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Hi Andy,
I appreciate your quick feedback!
I have done as you suggested and published my results this time using Google benchmark: https://github.com/nmoinvaz/strcasecmp
After you review it, and if you still think the patch is worthwhile then I can fix the other problems you mentioned for the original patch. If you think it is not worth it, then I understand.
Thanks again, Nathan
-----Original Message----- From: Andy Shevchenko <andy@kernel.org> Sent: Tuesday, October 25, 2022 2:04 AM To: Nathan Moinvaziri <nathan@nathanm.com> Cc: linux-kernel@vger.kernel.org Subject: Re: [PATCH] lib/string.c: Improve strcasecmp speed by not lowering if chars match
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
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