From mboxrd@z Thu Jan 1 00:00:00 1970 From: Stephan Diestelhorst Subject: Re: Hypervisor crash(!) on xl cpupool-numa-split Date: Wed, 2 Feb 2011 17:01:05 +0100 Message-ID: <201102021701.05665.stephan.diestelhorst@amd.com> References: <4D41FD3A.5090506@amd.com> <201102021539.06664.stephan.diestelhorst@amd.com> <4D4974D1.1080503@ts.fujitsu.com> Mime-Version: 1.0 Content-Type: text/plain; charset="iso-8859-1" Content-Transfer-Encoding: 7bit Return-path: In-Reply-To: <4D4974D1.1080503@ts.fujitsu.com> List-Unsubscribe: , List-Post: List-Help: List-Subscribe: , Sender: xen-devel-bounces@lists.xensource.com Errors-To: xen-devel-bounces@lists.xensource.com To: Juergen Gross Cc: George Dunlap , "Przywara, Andre" , Keir Fraser , "xen-devel@lists.xensource.com" , Ian Jackson List-Id: xen-devel@lists.xenproject.org On Wednesday 02 February 2011 16:14:25 Juergen Gross wrote: > On 02/02/11 15:39, Stephan Diestelhorst wrote: > > We have the following theory of what happens: > > * some vcpus of a particular domain are currently in the process of > > being moved to the new pool > > The only _vcpus_ to be moved between pools are the idle vcpus. And those > never contribute to accounting in credit scheduler. > > We are moving _pcpus_ only (well, moving a domain between pools actually > moves vcpus as well, but then the domain is paused). How do you ensure that the domain is paused and stays that way? Pausing the domain was what I had in mind, too... > > Despite the rant, it is amazing to see the ability to move running > > things around through this remote continuation trick! In my (ancient) > > balancer experiments I added hypervisor-threads just for side- > > stepping this issue.. > > I think the easiest way to solve the problem would be to move the cpu to the > new pool in a tasklet. This is possible now, because tasklets are always > executed in the idle vcpus. Yep. That was exactly what I build. At the time stuff like that did not exist (2005). > OTOH I'd like to understand what is wrong with my current approach... Nothing, in fact I like it. In my rant I complained about the fact that splitting the critical section accross this continuation looks scary, basically causing some generic red lights to turn on :-) And making reasoning about the correctness a little complicated, but that may well be a local issue ;-) Stephan -- Stephan Diestelhorst, AMD Operating System Research Center stephan.diestelhorst@amd.com Tel. +49 (0)351 448 356 719 Advanced Micro Devices GmbH Einsteinring 24 85609 Aschheim Germany Geschaeftsfuehrer: Alberto Bozzo u. Andrew Bowd; Sitz: Dornach, Gemeinde Aschheim, Landkreis Muenchen Registergericht Muenchen, HRB Nr. 43632, WEEE-Reg-Nr: DE 12919551