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-devel] Xen 4 TSC problems

To: Olivier Hanesse <olivier.hanesse@xxxxxxxxx>
Subject: Re: [Xen-devel] Xen 4 TSC problems
From: Keir Fraser <keir.xen@xxxxxxxxx>
Date: Thu, 24 Feb 2011 07:16:05 +0000
Cc: Dan Magenheimer <dan.magenheimer@xxxxxxxxxx>, xen-devel@xxxxxxxxxxxxxxxxxxx, Xen Users <xen-users@xxxxxxxxxxxxxxxxxxx>, Jeremy Fitzhardinge <jeremy@xxxxxxxx>, Mark Adams <mark@xxxxxxxxxxxxxxxxxx>
Delivery-date: Wed, 23 Feb 2011 23:17:11 -0800
Dkim-signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=gmail.com; s=gamma; h=domainkey-signature:user-agent:date:subject:from:to:cc:message-id :thread-topic:thread-index:in-reply-to:mime-version:content-type :content-transfer-encoding; bh=qy/7CEmzf085CgjORItt+kW5YpKd55LD96l+ctghku4=; b=xRpZbSVpZ2qYW5DtAwjpqHX9//BVMbD6iRbEfrekialCBBT81fTkpE7C+3AB3z9nQD c7i/wTnhD5DtSIxehC/8QIWcWpBbU6SQ+ZHjWtx/J2KRN2CKGhGKALzQsUVAHkEF3QhM n/nc/h+SmaIlXdWB4UDObkGHu1DxohjuByTdk=
Domainkey-signature: a=rsa-sha1; c=nofws; d=gmail.com; s=gamma; h=user-agent:date:subject:from:to:cc:message-id:thread-topic :thread-index:in-reply-to:mime-version:content-type :content-transfer-encoding; b=IzeGufHHVZ9C4RYWayTpdASKyw21XXNZf2Ei4eComsWKDaoGw0Gas4lOiem0RwWyOL S0YTaxnEAoLEi0fawCvVi8MAxCn0TR6knZbAgIuKICUr5BJnxra0JuwR/CHp5E1IPPZG 728Lb+4Ki0syAGHAzv/hMFBfW8QQHoG3BM22A=
Envelope-to: www-data@xxxxxxxxxxxxxxxxxxx
In-reply-to: <4D655A39.2040501@xxxxxxxxx>
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: AcvT8rMRfrxK+HBQuEKAIwfnCYe6wg==
Thread-topic: [Xen-devel] Xen 4 TSC problems
User-agent: Microsoft-Entourage/12.28.0.101117
Please send Xen boot output (xm dmesg). Getting it from Xen 3.2 as well
would be interesting, if you still have it installed on any of these
machines.

 -- Keir

On 23/02/2011 19:04, "Olivier Hanesse" <olivier.hanesse@xxxxxxxxx> wrote:

> I am sorry for the lack of information.
> Every domUs on the dom0 are affected by this bug at the exact same time.
> 
> And I had this bug on a dozen servers (all running on the same hw) since
> October (when I switched from Xen 3.2 to 4.0).
> 
> Regards
> 
> Olivier
> 
> Le 23/02/2011 18:19, Keir Fraser a écrit :
>> On 23/02/2011 16:16, "Dan Magenheimer"<dan.magenheimer@xxxxxxxxxx>  wrote:
>> 
>>> It¹s very unlikely this is a problem with TSC. It is most likely a Xen (or
>>> possibly a PV Linux) problem where a guest (or dom0) either ³goes out to
>>> lunch² for a long period, or some other timer gets stuck.  The ³clocksource
>>> tsc unstable² message is a side effect of this... it¹s very likely the TSC
>>> that IS stable and correct and the other clocksource (pvclock) has
>>> lost/gained
>>> 50 minutes!
>>> 
>>> Mark Adams cc¹ed and his original xen-devel posting below.  The fact that
>>> two
>>> different users (possibly on the same processor/system type?) have submitted
>>> the message with a delta so similar would lead me to believe there is some
>>> timer that is ³wrapping².  And since pvclock is usually the clocksource for
>>> dom0, and pvclock is driven!  by Xen¹s ³system time², a reasonable guess is
>>> that the timer that is wrapping is in Xen itself.
>>> 
>>> Mark¹s delta = -2999660303788 ns
>>> Your delta = -2999660334211 ns
>>> 
>>> Googling, I see the HPET wraparound is ~306 seconds and this delta is about
>>> 3000 seconds, so that may be a bad guess.
>>> 
>>> Keir, any thoughts on this?  Do you recall any post-4.0 patches that may
>>> have
>>> fixed this?
>> I've never seen a 3000s wrap, and I don't know of anything that would have
>> fixed a bug like this. If this is a Xen time wrap of some kind then it would
>> affect all running guests; it's not clear here whether only one, or all,
>> guests see the wrap.
>> 
>>   K.
>> 
>>> Thanks,
>>> Dan
>>> 
>>> References:
>>> http://lists.xensource.com/archives/html/xen-devel/2010-10/msg00210.html
>>> https://lkml.org/lkml/2010/10/26/126
>>> 
>>> 
>>> From: Olivier Hanesse [mailto:olivier.hanesse@xxxxxxxxx]
>>> Sent: Wednesday, February 23, 2011 3:50 AM
>>> To: xen-devel@xxxxxxxxxxxxxxxxxx!  m; Xen Users
>>> Subject: [Xen-devel] Xen 4 TSC problems
>>> 
>>> 
>>> Hello
>>> 
>>> 
>>> 
>>> I've got an issue about time keeping with Xen 4.0 (Debian squeeze release).
>>> 
>>> 
>>> 
>>> My problem is here (hopefully I amn't the only one, so there might be a bug
>>> somewhere) : http://bugs.debian.org/cgi-bin/bugreport.cgi?bug=599161#50
>>> 
>>> After some times,  I got this error : Clocksource tsc unstable (delta =
>>> -2999660334211 ns). It has happened on several servers.
>>> 
>>> 
>>> 
>>> Looking at the output of "xm debug-key s;"
>>> 
>>> 
>>> 
>>> (XEN) TSC has constant rate, deep Cstates possible, so not reliable,
>>> warp=2850
>>> (count=3)
>>> 
>>> 
>>> 
>>> I am using a "Intel(R) Xeon(R) CPU L5420  @ 2.50GHz", which has the
>>> "constant_tsc", but not the "nonstop_tsc" one.
>>> 
>>> On other systems with a newer cpu with "nonstop_tsc", I don't have this
>>> issue
>>> (systems are running the same distros with same config).
>>> 
>>> 
>>> 
>>> I tried to boot with "max_cstate=0", but nothing changed, my TSC isn't
>>> reliable and after some times, I will got the "50min" issue again.
>>> 
>>> 
>>> 
>>> I don't unders!  tand how a system can do a jump of "50min" in the future.
>>> Why
>>> 50min ? it is not 40min, not 1 hour, it is always 50min.
>>> 
>>> I don't know how to make my TSC "reliable" (I already disable everything
>>> about
>>> Powerstate in BIOS Settings).
>>> 
>>> 
>>> 
>>> Any ideas ?
>>> 
>>> 
>>> 
>>> Regards
>>> 
>>> 
>>> 
>>> Olivier
>>> 
>> 
> 



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