From mboxrd@z Thu Jan 1 00:00:00 1970 From: Jens Axboe Subject: Re: poor domU VBD performance. Date: Thu, 31 Mar 2005 20:01:52 +0200 Message-ID: <20050331180151.GT9204@suse.de> 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> <20050331165305.GA13875@vienna.egenera.com> Mime-Version: 1.0 Content-Type: text/plain; charset=us-ascii Return-path: Content-Disposition: inline In-Reply-To: <20050331165305.GA13875@vienna.egenera.com> List-Unsubscribe: , List-Post: List-Help: List-Subscribe: , Sender: xen-devel-bounces@lists.xensource.com Errors-To: xen-devel-bounces@lists.xensource.com To: Philip R Auld Cc: Ian Pratt , Xen development list , Kurt Garloff , Vincent Hanquez , Christian Limpach List-Id: xen-devel@lists.xenproject.org On Thu, Mar 31 2005, Philip R Auld wrote: > > > This effects merging though, right? I don't think the the front > > > end has done any merging. > > > > The noop elevator does front and back merging. > > My understanding is that it's used in the frontend driver. > > If that is the case, it can only merge things that are > machine contiguous. Current guests know this mapping, but > can they get this when running unmodified with VT-x. > > My experience showed very little if any multipage > IO coming out of the front end. There aren't that many users of multipage ios yet. direct io will use it, ext2 will as well. iirc, -mm has patches for ext3 too. so it's definitely improving :-) -- Jens Axboe