This is an archived copy of the Xen.org mailing list, which we have preserved to ensure that existing links to archives are not broken. The live archive, which contains the latest emails, can be found at http://lists.xen.org/
Home Products Support Community News


RE: [Xen-devel] HPET/PIT timer accuracy

To: "Benjamin LaHaise" <bcrl@xxxxxxxxx>
Subject: RE: [Xen-devel] HPET/PIT timer accuracy
From: "King, Steven R" <steven.r.king@xxxxxxxxx>
Date: Mon, 1 Aug 2005 14:02:07 -0700
Cc: xen-devel List <xen-devel@xxxxxxxxxxxxxxxxxxx>
Delivery-date: Tue, 02 Aug 2005 09:00:54 +0000
Envelope-to: www-data@xxxxxxxxxxxxxxxxxxx
List-help: <mailto:xen-devel-request@lists.xensource.com?subject=help>
List-id: Xen developer discussion <xen-devel.lists.xensource.com>
List-post: <mailto:xen-devel@lists.xensource.com>
List-subscribe: <http://lists.xensource.com/cgi-bin/mailman/listinfo/xen-devel>, <mailto:xen-devel-request@lists.xensource.com?subject=subscribe>
List-unsubscribe: <http://lists.xensource.com/cgi-bin/mailman/listinfo/xen-devel>, <mailto:xen-devel-request@lists.xensource.com?subject=unsubscribe>
Sender: xen-devel-bounces@xxxxxxxxxxxxxxxxxxx
Thread-index: AcWUpqxSQEUOcChnR9C/y8Ck7fKQnACM5OaQ
Thread-topic: [Xen-devel] HPET/PIT timer accuracy
The RDTSC instruction is out-of-order on Intel CPU's as well.  You can
place serializing instructions such as CPUID before and/or after RDTSC
to get better locality.  Unfortunately, CPUID expends many more cycles
than the RDTSC instruction on its own.

-----Original Message-----
From: xen-devel-bounces@xxxxxxxxxxxxxxxxxxx
[mailto:xen-devel-bounces@xxxxxxxxxxxxxxxxxxx] On Behalf Of Benjamin
Sent: Friday, July 29, 2005 6:33 PM
To: Ronald G. Minnich
Cc: Ian Pratt; xen-devel List
Subject: Re: [Xen-devel] HPET/PIT timer accuracy

On Fri, Jul 29, 2005 at 11:51:19AM -0600, Ronald G. Minnich wrote:
> I can only tell you we've seen weird numbers from the opteron tsc, to 
> the point that we don't entirely trust it. Not sure why.

Opterons can execute RDTSC out of order.

"Time is what keeps everything from happening all at once." -- John

Xen-devel mailing list

Xen-devel mailing list

<Prev in Thread] Current Thread [Next in Thread>