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-users

Re: [Xen-users] cpufreq problems with hvm

To: "Tian, Kevin" <kevin.tian@xxxxxxxxx>
Subject: Re: [Xen-users] cpufreq problems with hvm
From: Birger Brunswiek <birger.b@xxxxxxx>
Date: Thu, 24 Jul 2008 21:42:36 +0200
Cc: xen-users@xxxxxxxxxxxxxxxxxxx
Delivery-date: Thu, 24 Jul 2008 12:43:18 -0700
Envelope-to: www-data@xxxxxxxxxxxxxxxxxxx
In-reply-to: <D470B4E54465E3469E2ABBC5AFAC390F024D95CB@xxxxxxxxxxxxxxxxxxxxxxxxxxxx>
List-help: <mailto:xen-users-request@lists.xensource.com?subject=help>
List-id: Xen user discussion <xen-users.lists.xensource.com>
List-post: <mailto:xen-users@lists.xensource.com>
List-subscribe: <http://lists.xensource.com/mailman/listinfo/xen-users>, <mailto:xen-users-request@lists.xensource.com?subject=subscribe>
List-unsubscribe: <http://lists.xensource.com/mailman/listinfo/xen-users>, <mailto:xen-users-request@lists.xensource.com?subject=unsubscribe>
References: <48879B3F.7050306@xxxxxxx> <D470B4E54465E3469E2ABBC5AFAC390F024D95CB@xxxxxxxxxxxxxxxxxxxxxxxxxxxx>
Sender: xen-users-bounces@xxxxxxxxxxxxxxxxxxx
User-agent: Thunderbird 2.0.0.14 (Windows/20080421)
Tian, Kevin wrote:
From: Birger Brunswiek
Sent: 2008年7月24日 4:58

Hi all,
I was wondering if cpu frequency scaling in dom0 (using the cpufreq=dom0-kernel boot parameter) may cause problems with HVM domUs? This is on Xen 3.2.1.

PV domUs seem to work just fine. They adjust to the frequency change on the go. The HVM I run using the unmodified_driver drivers (also from the 3.2.1 release) seem to have very slow timers if dom0 lowers the frequency.


Current HVM can't cope with freq/tsc change, unless all rdtsc
are trapped which then may bring other side-effects for heavy
overhead. It's better for you to try cpufreq on a platform with
constant TSC, e.g. any Intel processors supporting VT.

I see ... it's just when the last time I looked for Intel CPUs it way quite difficult to get those with VT in the consumer segment. That's quite different with AMD.

Does anyone know if the modules (?) which are responsible to get the freq scaling right in PVs can be used/ported to an HVM? Similar to the unmodified drivers to use a paravirtualised disk and netif.

Birger

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

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