From: Nikolay Borisov <nborisov@suse.com>
To: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Linux Kernel Mailing List <linux-kernel@vger.kernel.org>,
Nick Desaulniers <ndesaulniers@google.com>,
linux-fsdevel <linux-fsdevel@vger.kernel.org>,
Dave Chinner <david@fromorbit.com>
Subject: Re: [PATCH] lib/string: Bring optimized memcmp from glibc
Date: Thu, 22 Jul 2021 11:28:56 +0300 [thread overview]
Message-ID: <80b4bbe8-2394-cfbb-ace1-9402169f5131@suse.com> (raw)
In-Reply-To: <CAHk-=wgMyXh3gGuSzj_Dgw=Gn_XPxGSTPq6Pz7dEyx6JNuAh9g@mail.gmail.com>
On 21.07.21 г. 21:45, Linus Torvalds wrote:
> On Wed, Jul 21, 2021 at 11:17 AM Nikolay Borisov <nborisov@suse.com> wrote:
>>
>> I find it somewhat arbitrary that we choose to align the 2nd pointer and
>> not the first.
>
> Yeah, that's a bit odd, but I don't think it matters.
>
> The hope is obviously that they are mutually aligned, and in that case
> it doesn't matter which one you aim to align.
>
>> So you are saying that the current memcmp could indeed use improvement
>> but you don't want it to be based on the glibc's code due to the ugly
>> misalignment handling?
>
> Yeah. I suspect that this (very simple) patch gives you the same
> performance improvement that the glibc code does.
You suspect correctly, perf profile:
30.44% -29.38% [kernel.vmlinux] [k] memcmp
This is only on x86-64 as I don't have other arch handy. But this one is
definitely good.
next prev parent reply other threads:[~2021-07-22 8:29 UTC|newest]
Thread overview: 23+ messages / expand[flat|nested] mbox.gz Atom feed top
2021-07-21 13:59 Nikolay Borisov
2021-07-21 14:32 ` Christoph Hellwig
2021-07-21 14:35 ` Nikolay Borisov
2021-07-21 14:42 ` Christoph Hellwig
2021-07-21 14:51 ` Matthew Wilcox
2021-07-21 15:17 ` Peter.Enderborg
2021-07-21 15:34 ` Matthew Wilcox
2021-07-21 15:39 ` Peter.Enderborg
2021-07-21 18:00 ` Linus Torvalds
2021-07-21 18:17 ` Nikolay Borisov
2021-07-21 18:45 ` Linus Torvalds
2021-07-21 18:55 ` Linus Torvalds
2021-07-21 19:26 ` Linus Torvalds
2021-07-22 11:28 ` Nikolay Borisov
2021-07-22 16:40 ` Linus Torvalds
2021-07-22 17:03 ` Nikolay Borisov
2021-08-26 9:03 ` Nikolay Borisov
2021-07-22 8:28 ` Nikolay Borisov [this message]
2021-07-23 14:02 ` David Laight
2021-07-21 20:10 ` David Sterba
2021-07-21 20:27 ` Linus Torvalds
2021-07-22 5:54 ` Nikolay Borisov
2021-07-28 20:12 ` Florian Weimer
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