From mboxrd@z Thu Jan 1 00:00:00 1970 From: Andrew Cooper Subject: Re: serious performance regression in Xen 4.2.4 and 4.2.5 Date: Thu, 19 Feb 2015 11:20:35 +0000 Message-ID: <54E5C703.7080703@citrix.com> References: <54E5C421.2060109@posteo.de> Mime-Version: 1.0 Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: 7bit Return-path: In-Reply-To: <54E5C421.2060109@posteo.de> List-Unsubscribe: , List-Post: List-Help: List-Subscribe: , Sender: xen-devel-bounces@lists.xen.org Errors-To: xen-devel-bounces@lists.xen.org To: Andreas Kinzler , xen-devel@lists.xen.org List-Id: xen-devel@lists.xenproject.org On 19/02/15 11:08, Andreas Kinzler wrote: > Hello Xen developers, > > since we use Xen for our production systems, I run many tests on Xen > (stability/performance). One test now uncovered a serious performance > regression when updating from Xen 4.2.3 to 4.2.x (with x>=4). To > reproduce run a domU (HVM) and compile a kernel for example ("time > make -j3"). Below are my results - compilation times more than double! > > Is it my mistake or otherwise how could such a bug be unnoticed? > Really wondering. > If it is really a regression, will it be fixed since the 4.2 branch is > declared unsupported? > > Regards Andreas > > Xen 4.2.3, 3.10.44-el7-pvops0-ak3, Xeon E3-1230, compile in HVM > real 2m58.371s > user 5m11.580s > sys 0m12.736s > > Xen 4.2.4, 3.10.44-el7-pvops0-ak3, Xeon E3-1230, compile in HVM > real 6m44.697s (!!!) > user 12m4.988s > sys 0m33.916s > > Xen 4.2.5, 3.10.44-el7-pvops0-ak3, Xeon E3-1230, compile in HVM > real 6m27.998s (!!!) > user 11m42.664s > sys 0m32.700s > > Is it perhaps http://xenbits.xen.org/gitweb/?p=xen.git;a=commitdiff;h=f1e0df14412ccc6933a68eda66ac5b7d89186b62 ? There are a number of correctness fixes in that range which will adversely affect performance. ~Andrew