linux-kernel - Re: [PATCH v2] x86: bring back rep movsq for user access on CPUs without ERMS

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Message-ID: <CAHk-=wg6bzTdQHSsswHPYFUbb1DfszyWTZ97hZv7bYxaNHVkHw@mail.gmail.com>
Date:   Sun, 3 Sep 2023 13:08:03 -0700
From:   Linus Torvalds <torvalds@...ux-foundation.org>
To:     Mateusz Guzik <mjguzik@...il.com>
Cc:     linux-kernel@...r.kernel.org, linux-arch@...r.kernel.org,
        bp@...en8.de
Subject: Re: [PATCH v2] x86: bring back rep movsq for user access on CPUs
 without ERMS

On Sun, 3 Sept 2023 at 11:49, Linus Torvalds
<torvalds@...ux-foundation.org> wrote:
>
> So I have no idea why you claim that "currently they have no choice".
> glibc is simply being incredibly stupid, and using newfstatat() for no
> good reason.

Do you have any good benchmark that shows the effects of this?

And if you do, does the attached patch (ENTIRELY UNTESTED!) fix the
silly glibc mis-feature?

               Linus

View attachment "patch.diff" of type "text/x-patch" (662 bytes)