From mboxrd@z Thu Jan 1 00:00:00 1970 From: Konrad Rzeszutek Wilk Subject: Re: Disk iops performance scalability Date: Tue, 19 Mar 2013 08:58:03 -0400 Message-ID: <20130319125802.GA2706@phenom.dumpdata.com> References: <5B6A896C-D23D-49E1-8214-A5E63D190620@clustered.net> Mime-Version: 1.0 Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: 7bit Return-path: Content-Disposition: inline In-Reply-To: <5B6A896C-D23D-49E1-8214-A5E63D190620@clustered.net> List-Unsubscribe: , List-Post: List-Help: List-Subscribe: , Sender: xen-devel-bounces@lists.xen.org Errors-To: xen-devel-bounces@lists.xen.org To: John Morrison Cc: xen-devel@lists.xen.org List-Id: xen-devel@lists.xenproject.org On Mon, Mar 18, 2013 at 11:23:00PM +0000, John Morrison wrote: > Hi, > > Seeing a drop-off in iops when more vcpu's are added:- > > 3.8.2 kernel/xen-4.2.1/single domU/LVM backend/8GB RAM domU/2GB RAM dom0 > > dom0_max_vcpus=2 dom0_vcpus_pin > > domU 8 cores fio result 145k iops > domU 10 cores fio result 99k iops > domU 12 cores fio result 89k iops > domU 14 cores fio result 81k iops > > ioping . -c 3 > 4096 bytes from . (ext4 /dev/xvda1): request=1 time=0.1 ms > 4096 bytes from . (ext4 /dev/xvda1): request=2 time=0.7 ms > 4096 bytes from . (ext4 /dev/xvda1): request=3 time=0.8 ms > > --- . (ext4 /dev/xvda1) ioping statistics --- > 3 requests completed in 2002.0 ms, 1836 iops, 7.2 mb/s > min/avg/max/mdev = 0.1/0.5/0.8/0.3 ms > > The initial ioping response is good, then a lot of latency with later ones. Any ideas ? Is your guest compiled with PARAVIRT_SPINLOCK and are you using a PV or PVHVM guest? > > Thanks > > John > > _______________________________________________ > Xen-devel mailing list > Xen-devel@lists.xen.org > http://lists.xen.org/xen-devel >