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In-Reply-To: <87sfsuak62.fsf@oldenburg.str.redhat.com>
From: "H.J. Lu" <hjl.tools@gmail.com>
Date: Mon, 7 Feb 2022 05:27:55 -0800
Message-ID: <CAMe9rOqhH=uHqEF+99vdHKqGV0q0wP__-03m-3chUjhvWibgpg@mail.gmail.com>
Subject: Re: [PATCH] elf: Replace memcmp with __memcmpeq for variable size
To: Florian Weimer <fweimer@redhat.com>
Cc: "H.J. Lu via Libc-alpha" <libc-alpha@sourceware.org>
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On Mon, Feb 7, 2022 at 5:19 AM Florian Weimer <fweimer@redhat.com> wrote:
>
> * H. J. Lu:
>
> >> This must be something else.  According to the numbers, we save ~159
> >> between ~569 cycles per __memcmpeq call.  That is just not realistic.
> >
> > I removed the cycle info from the commit log.
>
> If we can't show the change is beneficial, is it worth the additional
> 1000 or so bytes in the loader text?
>

$ LD_DEBUG=statistics elf/tst-relsort1 --direct

does show improvements when __memcmpeq is called 24 times.
But the cycle number changes for each run.  The overall trend is
faster.  It will be more obvious when memcmp is called more often.

-- 
H.J.