linux-kernel - Re: [PATCH] x86: handle the tail in rep_movs_alternative() with an overlapping store

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Message-ID: <CAHk-=wjo__Bj3JNw_7E8HhTDUF65LVOApvN0D2cofgotJoqpmg@mail.gmail.com>
Date: Thu, 20 Mar 2025 14:17:17 -0700
From: Linus Torvalds <torvalds@...ux-foundation.org>
To: Mateusz Guzik <mjguzik@...il.com>
Cc: x86@...nel.org, hkrzesin@...hat.com, tglx@...utronix.de, mingo@...hat.com, 
	bp@...en8.de, dave.hansen@...ux.intel.com, hpa@...or.com, olichtne@...hat.com, 
	atomasov@...hat.com, aokuliar@...hat.com, linux-kernel@...r.kernel.org
Subject: Re: [PATCH] x86: handle the tail in rep_movs_alternative() with an
 overlapping store

On Thu, 20 Mar 2025 at 12:33, Mateusz Guzik <mjguzik@...il.com> wrote:
>
> I have a recollection that handling the tail after rep movsq with an
> overlapping store was suffering a penalty big enough to warrant a
> "normal" copy instead, avoiding the just written to area.

Ahh. Good point. The rep movsq might indeed end up having odd effects
with subsequent aliasing memory operations.

Consider myself convinced.

           Linus