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] Re: [Xen-users] About profiling xen

To: Marco Tizzoni <marco.tizzoni@xxxxxxxxx>, "Pasi Kärkkäinen" <pasik@xxxxxx>
Subject: RE: [Xen-devel] Re: [Xen-users] About profiling xen
From: Dan Magenheimer <dan.magenheimer@xxxxxxxxxx>
Date: Wed, 30 Sep 2009 07:21:25 -0700 (PDT)
Cc: "Fajar A." <fajar@xxxxxxxxx>, Fasiha Ashraf <feehapk@xxxxxxxxxxx>, xen <xen-devel@xxxxxxxxxxxxxxxxxxx>, xen-users@xxxxxxxxxxxxxxxxxxx
Delivery-date: Wed, 30 Sep 2009 07:22:40 -0700
Envelope-to: www-data@xxxxxxxxxxxxxxxxxxx
In-reply-to: <f9611b0f0909300206v53577d1cw300ff6092b8ffede@xxxxxxxxxxxxxx>
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>
Sender: xen-users-bounces@xxxxxxxxxxxxxxxxxxx
> Is there a way to make available a better timer (hpet,acpi....)?
> Also, on another xen box (rhel 5.2), I've a 'pit' clocksource in
> available_clocksource.
> After:
> # sysctl -w xen.independent_wallclock=1
> and
> --------------------------------------------------------------
> ----------------------------------------------------------------------
> # echo pit > 
> /sys/devices/system/clocksource/clocksource0/current_clocksource
> [root@station1 init.d]# cat
> /sys/devices/system/clocksource/clocksource0/current_clocksource
> jiffies
> --------------------------------------------------------------
> ----------------------------------------------------------------------
> the clocksource is unmodified.

Because of save/restore and migrate, no hardware timer is
suitable for a pv domain.  The code that is handling the
clock is the paravirtualized clock code (aka pvclock).
Nobody ever changed the sysfs reporting mechanism in
pv versions of released Red Hat kernels, so clocksource
gets reported as "jiffies", and even though "pit"
appears to be available, it is not (since it wouldn't
work).  I suspect this is also the case for other
distros' pv kernels.


Xen-users mailing list