From mboxrd@z Thu Jan 1 00:00:00 1970 From: Andrew Cooper Subject: Re: Strange interdependace between domains Date: Fri, 14 Feb 2014 13:26:19 +0000 Message-ID: <52FE197B.7090609@citrix.com> References: <1646915994.20140213165604@gmail.com> <1392313015.32038.112.camel@Solace> <295276356.20140213222507@gmail.com> <6010385428.20140214120238@gmail.com> Mime-Version: 1.0 Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: 7bit Return-path: In-Reply-To: <6010385428.20140214120238@gmail.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: Simon Martin Cc: Ian Campbell , Dario Faggioli , Nate Studer , Don Slutz , xen-devel@lists.xen.org List-Id: xen-devel@lists.xenproject.org On 14/02/14 12:02, Simon Martin wrote: > Hello Simon, > > Thanks everyone and especially Ian! It was the hyperthreading that was > causing the problem. > > Here's my current configuration: > > # xl cpupool-list -c > Name CPU list > Pool-0 0,1 > pv499 2,3 > # xl vcpu-list > Name ID VCPU CPU State Time(s) CPU Affinity > Domain-0 0 0 0 r-- 16.6 0 > Domain-0 0 1 1 -b- 7.3 1 > win7x64 1 0 1 -b- 82.5 all > win7x64 1 1 0 -b- 18.6 all > pv499 2 0 3 r-- 226.1 3 > > I have pinned dom0 as I wasn't sure whether it belongs to Pool-0 (I > assume it does, can you confirm please). > > Dario, if you are going to look at the > > Looking at my timings with this configuration I am seeing a 1% > variation (945 milliseconds +/- 5). I think this can be attributable > to RAM contention, at the end of the day all cores are competing for > the same bus. > There is also things such as the Xen time calibration rendezvous which a synchronisation point of all online cpus, once per second. Having any single cpu slow to enter the rendezvous will delay all others which have already entered. This will likely add a bit of jitter if one cpu in xen is doing a lengthy operation with interrupts disabled at the point at which the rendezvous is triggered. ~Andrew