From mboxrd@z Thu Jan 1 00:00:00 1970 From: Konrad Rzeszutek Wilk Subject: Re: a strange issue on disk scheduler in xen Date: Fri, 15 Mar 2013 09:23:59 -0400 Message-ID: <20130315132358.GJ8582@phenom.dumpdata.com> References: <1363243207173-5714815.post@n5.nabble.com> Mime-Version: 1.0 Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: 7bit Return-path: Content-Disposition: inline In-Reply-To: <1363243207173-5714815.post@n5.nabble.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: smiler Cc: xen-devel@lists.xensource.com List-Id: xen-devel@lists.xenproject.org On Wed, Mar 13, 2013 at 11:40:07PM -0700, smiler wrote: > Hi all, > > In Xen 4.0 with Linux 2.6.18.8, noop is default scheduler in dom U. In Xen > 4.0 with Linux 2.6.31.8, CFQ is default scheduler in domU. In the both > setup, CFQ is default scheduler in dom0. I compare the execution time of two > seqenatil read applications run on a domU under noop of domU with under cfq > of domU in both two Linux kernel. > The sequential read application is generated by sysbench to read 1gb, like > that: sysbench --num-threads=16 --test=fileio --file-total-size=1G > --file-test-mode=seqrd prepare/run/cleanup > > I find a strange phenomenon as following: > in Xen 4.0 with Linux 2.6.18.8 > noop in domU > seqrd 1: 34.90s seqrd2: 32.49s > cfq in domU > seqrd 1: 245.94s seqrd2: 256.09s > In this situation, the execution time of seqrd under CFQ of domU is much > worse than that under noop of domU. > However, in Xen 4.0 with Linux 2.6.31.8: > noop in domU > seqrd1: 36.83s seqrd 2: 37.01s > CFQ in domU > seqrd1: 35.68s seqrd 2: 35.76s > In this situation, the execution time of seqrd under CFQ of domU is almost > same as under noop of domU. > > The comparsion between noop and cfq of domU in Xen 4.0 with Linux 2.6.18 is > so different from that in Xen 4.0 with Linux 2.6.31.8, It is very very > strange. I also do the experiment in differnt machines, the results are > same. So does anyone know the reason? You are using ancient code. It might be very well that there were bugs in 2.6.18. > > > > -- > View this message in context: http://xen.1045712.n5.nabble.com/a-strange-issue-on-disk-scheduler-in-xen-tp5714815.html > Sent from the Xen - Dev mailing list archive at Nabble.com. > > _______________________________________________ > Xen-devel mailing list > Xen-devel@lists.xen.org > http://lists.xen.org/xen-devel >