WARNING - OLD ARCHIVES

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/
   
 
 
Xen 
 
Home Products Support Community News
 
   
 

xen-devel

Re: [Xen-devel] write_tsc in a PV domain?

To: Dan Magenheimer <dan.magenheimer@xxxxxxxxxx>, Jeremy Fitzhardinge <jeremy@xxxxxxxx>
Subject: Re: [Xen-devel] write_tsc in a PV domain?
From: Keir Fraser <keir.fraser@xxxxxxxxxxxxx>
Date: Mon, 31 Aug 2009 20:06:02 +0100
Cc: "Xen-Devel \(E-mail\)" <xen-devel@xxxxxxxxxxxxxxxxxxx>, Alan Cox <alan@xxxxxxxxxxxxxxxxxxx>
Delivery-date: Mon, 31 Aug 2009 12:06:36 -0700
Envelope-to: www-data@xxxxxxxxxxxxxxxxxxx
In-reply-to: <25b28950-8720-4d8f-a88a-bae8ffe6e602@default>
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/mailman/listinfo/xen-devel>, <mailto:xen-devel-request@lists.xensource.com?subject=subscribe>
List-unsubscribe: <http://lists.xensource.com/mailman/listinfo/xen-devel>, <mailto:xen-devel-request@lists.xensource.com?subject=unsubscribe>
Sender: xen-devel-bounces@xxxxxxxxxxxxxxxxxxx
Thread-index: AcoqZo+1DdtLBxzcQK24QKYKl17krwAB4VDL
Thread-topic: [Xen-devel] write_tsc in a PV domain?
User-agent: Microsoft-Entourage/12.20.0.090605
On 31/08/2009 19:11, "Dan Magenheimer" <dan.magenheimer@xxxxxxxxxx> wrote:

> I have yet to get a measurement of either syscall that
> is better than 2.5x WORSE than emulating rdtsc. On
> my dual-core Conroe (Intel E6850) with 64-bit Xen and
> 32-bit dom0, I get approximately:
> 
> rdtsc native: 22ns
> softtsc (rdtsc emulated): 360ns

Trap-and-emulate in 360ns seems astoundingly good. Perhaps too good to be
true?

 -- Keir



_______________________________________________
Xen-devel mailing list
Xen-devel@xxxxxxxxxxxxxxxxxxx
http://lists.xensource.com/xen-devel