From mboxrd@z Thu Jan 1 00:00:00 1970 From: Andreas Kinzler Subject: Re: Questions about GPLPV stability tests Date: Wed, 30 Nov 2011 14:11:48 +0100 Message-ID: <4ED62B94.4040502@hfp.de> References: <4ED51291.1010308@hfp.de> <4ED5215D.1010403@hfp.de> Mime-Version: 1.0 Content-Type: text/plain; charset="us-ascii"; Format="flowed" Content-Transfer-Encoding: 7bit Return-path: In-Reply-To: List-Unsubscribe: , List-Post: List-Help: List-Subscribe: , Sender: xen-devel-bounces@lists.xensource.com Errors-To: xen-devel-bounces@lists.xensource.com To: Roderick Colenbrander Cc: xen-devel@lists.xensource.com List-Id: xen-devel@lists.xenproject.org >> The patch actually only disables HPET broadcast which has some downsides >> because it effectively disables C3 states. Without C3 states Nehalem and >> later CPUs cannot enter turbo-mode. So there is some loss of performance. > Would disabling any low CPU power states and turbo clocks in the BIOS, > help as well? Just curious. I have seen other 'weird' performance I would leave the BIOS to its default and I'd guess that playing with BIOS settings only makes it worse. > issues between machines using the same hardware. Some CPU intensive > algorithm could be twice as slow running on Dom0 compared to the same > kernel without Xen. On other identical systems I didn't see that > issue. I didn't have time to investigate, but I felt there may have > been BIOS setting differences. Xen does not use the performance governor by default which has a notable performance impact in my tests. My Xen boot config is: kernel /xen.gz dom0_mem=1024m dom0_max_vcpus=2 cpufreq=xen:performance module /linux-2.6.32.36-pvops0-ak2 root=/dev/sda5 Regards Andreas