From: Adhemerval Zanella Netto <adhemerval.zanella@linaro.org>
To: Xi Ruoyao <xry111@xry111.site>,
libc-alpha@sourceware.org, DJ Delorie <dj@redhat.com>
Subject: Re: posix_memalign performance regression in 2.38?
Date: Fri, 4 Aug 2023 11:12:44 -0300 [thread overview]
Message-ID: <067bed0b-87f6-abbb-0e2a-14ee1a0ac0f9@linaro.org> (raw)
In-Reply-To: <68e8c4eb66697f2f2cd37bf9456b60aabf7e1bc5.camel@xry111.site>
On 03/08/23 23:52, Xi Ruoyao via Libc-alpha wrote:
> Hi,
>
> There seems a performance regression of posix_memalign in Glibc-2.38:
>
> $ cat t.c
> #include <stdlib.h>
> int main()
> {
> void *buf;
> for (int i = 0; i < (1 << 16); i++)
> posix_memalign(&buf, 64, 16);
> }
> $ cc t.c
> $ time ./a.out
>
> real 0m0.008s
> user 0m0.005s
> sys 0m0.003s
> $ time ~/sources/lfs/glibc-2.38/build/testrun.sh ./a.out
>
> real 0m4.376s
> user 0m4.369s
> sys 0m0.007s
>
> The behavior seems worse than quadratic: if I change "1 << 16" to "1 <<
> 17", I get:
>
> $ time ~/sources/lfs/glibc-2.38/build/testrun.sh ./a.out
>
> real 0m28.597s
> user 0m28.568s
> sys 0m0.022s
>
> I've not bisected for this yet.
>
It seems to be caused by 24cdd6c71debfd10a9f7cb217fe2a2c4c486ed6f, where
posix_memalign now calls chunk_ok_for_memalign (which takes most of time).
DJ, any idea on how we can improve this?
next prev parent reply other threads:[~2023-08-04 14:12 UTC|newest]
Thread overview: 12+ messages / expand[flat|nested] mbox.gz Atom feed top
2023-08-04 2:52 Xi Ruoyao
2023-08-04 14:12 ` Adhemerval Zanella Netto [this message]
2023-08-07 19:49 ` DJ Delorie
2023-08-07 19:57 ` Sam James
2023-08-07 20:15 ` DJ Delorie
2023-08-08 3:38 ` DJ Delorie
2023-08-08 8:08 ` Xi Ruoyao
2023-08-08 15:08 ` DJ Delorie
2023-08-09 10:47 ` Florian Weimer
2023-08-09 16:59 ` Florian Weimer
2023-08-07 19:58 ` Noah Goldstein
2023-08-07 20:07 ` DJ Delorie
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