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Message-ID: <20061115190308.GA9303@elte.hu>
Date: Wed, 15 Nov 2006 20:03:08 +0100
From: Ingo Molnar <mingo@...e.hu>
To: Jeremy Fitzhardinge <jeremy@...p.org>
Cc: Arjan van de Ven <arjan@...radead.org>, akpm@...l.org, ak@...e.de,
linux-kernel@...r.kernel.org, Michael.Fetterman@...cam.ac.uk,
Ian Campbell <Ian.Campbell@...Source.com>
Subject: Re: i386 PDA patches use of %gs
* Jeremy Fitzhardinge <jeremy@...p.org> wrote:
> Ingo Molnar wrote:
> > i'd not even use glibc's %gs but set up two separate selectors.
> > (that's a more controlled experiment - someone might run a non-TLS
> > glibc, etc.)
> >
>
> Well, in that case they probably don't care whether the kernel uses
> %fs or %gs ;)
>
> But either way, this doesn't have much bearing on Eric's test; we'd be
> only talking about a few ns per kernel exit, rather than 5% for
> read/write.
if the timings are different then it very much has bearing on the
argument that i made against the current i386 PDA patchset, that mixed
use segments are suboptimal.
So i'm NAK-ing the i386 PDA patchset until this has been properly
measured (and fixed if needed).
Ingo
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