From mboxrd@z Thu Jan 1 00:00:00 1970 From: Juergen Gross Subject: Re: [PATCH] libxl: Make 'xl vcpu-set' work properly on overcommited hosts. Date: Mon, 13 May 2013 07:00:07 +0200 Message-ID: <51907357.3070900@ts.fujitsu.com> References: <1367959244-5413-1-git-send-email-konrad.wilk@oracle.com> <1368009999.26321.223.camel@zakaz.uk.xensource.com> <20130508142903.GA9314@phenom.dumpdata.com> <1368025493.17285.18.camel@zakaz.uk.xensource.com> <20130508163550.GC369@phenom.dumpdata.com> <1368031774.17285.49.camel@zakaz.uk.xensource.com> <20130508170515.GA1184@phenom.dumpdata.com> <1368040183.3756.17.camel@dagon.hellion.org.uk> <20130508223911.GA9226@phenom.dumpdata.com> Mime-Version: 1.0 Content-Type: text/plain; charset="us-ascii"; Format="flowed" Content-Transfer-Encoding: 7bit Return-path: In-Reply-To: <20130508223911.GA9226@phenom.dumpdata.com> List-Unsubscribe: , List-Post: List-Help: List-Subscribe: , Sender: xen-devel-bounces@lists.xen.org Errors-To: xen-devel-bounces@lists.xen.org To: Konrad Rzeszutek Wilk Cc: George Dunlap , "xen-devel@lists.xensource.com" , Ian Jackson , Ian Campbell List-Id: xen-devel@lists.xenproject.org On 09.05.2013 00:39, Konrad Rzeszutek Wilk wrote: >>>>> Well, overcommit comes in mind. Say you migrate to a 4PCPU box and you >>>>> have 12VCPUs, then you decide to go down to 4, then back to 16 before >>>>> migrating it to some other box. Can't do. >>>> >>>> You could do it *after* the migration back to a 16 way box n stead of >>>> before though, which is most likely when you would actually want to do >>>> it... >>> >>> I am kind of lost. Are we arguing for this being a bug or whether there is >>> justification for putting in Xen 4.3? >> >> The former needs deciding before the latter. >> >> I'm not convinced that the current xl behaviour of refusing to >> overcommit VCPUs on a host isn't the right one for the majority of use >> cases. Obviously the silently refusing bit is a bug which should be >> fixed. >> >> I don't buy that this is a "regression compared to Xend". It's certainly >> a difference from how xend behaved but it seems on the whole to be a >> positive one (i.e. xend was wrong). > > CC-ing Juergen here as he added this in. I surely didn't mean to disable overcommitting. So I'm fine with your patch to do the cpumap allocation with maxvcpus. Juergen -- Juergen Gross Principal Developer Operating Systems PBG PDG ES&S SWE OS6 Telephone: +49 (0) 89 3222 2967 Fujitsu Technology Solutions e-mail: juergen.gross@ts.fujitsu.com Domagkstr. 28 Internet: ts.fujitsu.com D-80807 Muenchen Company details: ts.fujitsu.com/imprint.html