From: "H. Peter Anvin" <hpa@zytor.com>
To: Tejun Heo <tj@kernel.org>
Cc: Jeremy Fitzhardinge <jeremy@goop.org>,
mingo@redhat.com, linux-kernel@vger.kernel.org,
jeremy.fitzhardinge@citrix.com, stable@kernel.org,
tglx@linutronix.de, mingo@elte.hu,
linux-tip-commits@vger.kernel.org
Subject: Re: [tip:x86/asm] x86/i386: Make sure stack-protector segment base is cache aligned
Date: Thu, 03 Sep 2009 20:35:37 -0700 [thread overview]
Message-ID: <4AA08B09.50503@zytor.com> (raw)
In-Reply-To: <4AA08283.5020306@kernel.org>
On 09/03/2009 07:59 PM, Tejun Heo wrote:
>
> Another question. Other than saving and loading an extra segment
> register on kernel entry/exit, whether using the same or different
> segment registers doesn't look like would make difference
> performance-wise. If I'm interpreting the wording in the optimization
> manual correctly, it means that each non-zero segment based memory
> access will be costly regardless of which specific segment register is
> in use and there's no way we can merge segment based dereferences for
> stackprotector and percpu variables.
>
It's correct that it doesn't make any difference for access, only for load.
-hpa
--
H. Peter Anvin, Intel Open Source Technology Center
I work for Intel. I don't speak on their behalf.
next prev parent reply other threads:[~2009-09-04 3:40 UTC|newest]
Thread overview: 29+ messages / expand[flat|nested] mbox.gz Atom feed top
2009-09-03 19:27 [PATCH] x86/i386: make sure stack-protector segment base is cache aligned Jeremy Fitzhardinge
2009-09-03 19:47 ` Eric Dumazet
2009-09-03 20:41 ` Jeremy Fitzhardinge
2009-09-03 21:07 ` Eric Dumazet
2009-09-03 21:31 ` Jeremy Fitzhardinge
2009-09-04 7:58 ` [tip:x86/asm] x86/i386: Put aligned stack-canary in percpu shared_aligned section tip-bot for Jeremy Fitzhardinge
2009-09-03 20:03 ` [tip:x86/asm] x86/i386: Make sure stack-protector segment base is cache aligned tip-bot for Jeremy Fitzhardinge
2009-09-03 20:26 ` H. Peter Anvin
2009-09-03 20:45 ` Jeremy Fitzhardinge
2009-09-03 21:15 ` H. Peter Anvin
2009-09-03 21:18 ` Ingo Molnar
2009-09-03 21:21 ` H. Peter Anvin
2009-09-04 14:15 ` Arjan van de Ven
2009-09-04 15:59 ` Jeremy Fitzhardinge
2009-09-04 16:06 ` H. Peter Anvin
2009-09-03 21:28 ` Jeremy Fitzhardinge
2009-09-04 2:51 ` Tejun Heo
2009-09-04 2:59 ` Tejun Heo
2009-09-04 3:35 ` H. Peter Anvin [this message]
2009-09-04 3:47 ` Tejun Heo
2009-09-04 3:51 ` H. Peter Anvin
2009-09-04 5:06 ` Tejun Heo
2009-09-04 5:12 ` Ingo Molnar
2009-09-04 16:04 ` Jeremy Fitzhardinge
2009-09-04 16:09 ` Tejun Heo
2009-09-04 16:13 ` H. Peter Anvin
2009-09-04 16:01 ` Jeremy Fitzhardinge
2009-09-04 16:52 ` H. Peter Anvin
2009-09-04 16:57 ` Jeremy Fitzhardinge
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