From: Andi Kleen <ak@suse.de>
To: Arjan van de Ven <arjan@linux.intel.com>
Cc: linux-kernel@vger.kernel.org, akpm@osdl.org
Subject: Re: [patch] Mark rdtsc as sync only for netburst, not for core2
Date: Tue, 28 Nov 2006 11:36:28 +0100 [thread overview]
Message-ID: <200611281136.29066.ak@suse.de> (raw)
In-Reply-To: <1164709708.3276.72.camel@laptopd505.fenrus.org>
On Tuesday 28 November 2006 11:28, Arjan van de Ven wrote:
> Hi,
>
> On the Core2 cpus, the rdtsc instruction is not serializing (as defined
> in the architecture reference since rdtsc exists) and due to the deep
> speculation of these cores, it's possible that you can observe time go
> backwards between cores due to this speculation. Since the kernel
> already deals with this with the SYNC_RDTSC flag, the solution is
> simple, only assume that the instruction is serializing on family 15...
>
> The price one pays for this is a slightly slower gettimeofday (by a
> dozen or two cycles), but that increase is quite small to pay for a
> really-going-forward tsc counter.
Added thanks
-Andi
next prev parent reply other threads:[~2006-11-28 10:41 UTC|newest]
Thread overview: 7+ messages / expand[flat|nested] mbox.gz Atom feed top
2006-11-28 10:28 [patch] Mark rdtsc as sync only for netburst, not for core2 Arjan van de Ven
2006-11-28 10:36 ` Andi Kleen [this message]
[not found] ` <1164774239.15257.5.camel@ymzhang>
2006-11-29 7:30 ` Arjan van de Ven
2006-11-29 8:05 ` Nick Piggin
2006-11-29 9:04 ` Zhang, Yanmin
[not found] ` <1164787104.2899.7.camel@ymzhang>
2006-11-29 8:35 ` Arjan van de Ven
2006-11-29 9:07 ` Zhang, Yanmin
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