From mboxrd@z Thu Jan  1 00:00:00 1970
From: Andreas Kinzler <ml-ak@posteo.de>
Subject: serious performance regression in Xen 4.2.4 and 4.2.5
Date: Thu, 19 Feb 2015 12:08:17 +0100
Message-ID: <54E5C421.2060109@posteo.de>
Mime-Version: 1.0
Content-Type: text/plain; charset="us-ascii"; Format="flowed"
Content-Transfer-Encoding: 7bit
Return-path: <xen-devel-bounces@lists.xen.org>
List-Unsubscribe: <http://lists.xen.org/cgi-bin/mailman/options/xen-devel>,
	<mailto:xen-devel-request@lists.xen.org?subject=unsubscribe>
List-Post: <mailto:xen-devel@lists.xen.org>
List-Help: <mailto:xen-devel-request@lists.xen.org?subject=help>
List-Subscribe: <http://lists.xen.org/cgi-bin/mailman/listinfo/xen-devel>,
	<mailto:xen-devel-request@lists.xen.org?subject=subscribe>
Sender: xen-devel-bounces@lists.xen.org
Errors-To: xen-devel-bounces@lists.xen.org
To: xen-devel@lists.xen.org
List-Id: xen-devel@lists.xenproject.org

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