From mboxrd@z Thu Jan 1 00:00:00 1970 From: Andrew Theurer Subject: Re: poor domU VBD performance. Date: Thu, 31 Mar 2005 10:02:07 -0600 Message-ID: <424C1EFF.3060206@us.ibm.com> References: <20050331070514.GH9204@suse.de> <20050331071043.GI9204@suse.de> <63537e2b84ddbba6cb3d970f73c6ab35@cl.cam.ac.uk> <20050331081900.GK9204@suse.de> <20050331143312.GB13179@vienna.egenera.com> <20050331153449.GE12579@tpkurt.garloff.de> <20050331153925.GP9204@suse.de> Mime-Version: 1.0 Content-Type: text/plain; charset=ISO-8859-1; 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: Keir Fraser Cc: Ian Pratt , Philip R Auld , Kurt Garloff , Xen development list , Vincent Hanquez , Jens Axboe , Christian Limpach List-Id: xen-devel@lists.xenproject.org Keir Fraser wrote: > > On 31 Mar 2005, at 16:39, Jens Axboe wrote: > >> Not necessarily - either your io rate is not fast enough to sustain a >> substantial queue depth, in that case you get plugging on basically >> every io anyways. If on the other hand the io rate is high enough to >> maintain a queue depth of > 1, then the plugging will never take place >> because the queue never empties. >> >> So all in all, I don't think the temporary work-around will be such a >> bad idea. I would still rather implement the queue tracking though, it >> should not be more than a few lines of code. > > > I've checked in something along the lines of what you described into > both the 2.0-testing and the unstable trees. Looks to have identical > performance to the original simple patch, at least for a bulk 'dd'. I'll do a pull of unstable and see what I get with o_direct, thanks. -Andrew