From mboxrd@z Thu Jan 1 00:00:00 1970 From: Daniel Veillard Subject: Re: VT is comically slow Date: Mon, 3 Jul 2006 06:31:40 -0400 Message-ID: <20060703103140.GW1483@redhat.com> References: <44A8D54A.3000100@redhat.com> <44A8D9F9.4020603@redhat.com> <04a32acd46c25a206dbc3404749f9a13@cl.cam.ac.uk> Reply-To: veillard@redhat.com Mime-Version: 1.0 Content-Type: text/plain; charset=us-ascii Return-path: Content-Disposition: inline In-Reply-To: <04a32acd46c25a206dbc3404749f9a13@cl.cam.ac.uk> 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: xen-devel@lists.xensource.com List-Id: xen-devel@lists.xenproject.org On Mon, Jul 03, 2006 at 09:58:01AM +0100, Keir Fraser wrote: > > On 3 Jul 2006, at 09:48, Rik van Riel wrote: > > >Looking at it a bit more closely, it appears that postgresql > >doing disk IO from inside a fully virtualized domain totally > >kills the CPU. > > > >It gets so bad that a simple "dmesg" takes 10-20 seconds to start, > >and after that it spews data maybe 7 or 8 lines every other second. > >Actually slower than serial console... > > > >This is totally unusable :( > > Might you be emulating PIO? That would certainly suck. The device model > is supposed to support (virtual) DMA though. That's the first thing I though about but apparently the kernel runs the IDE device in DMA mode if one believe the hdparm output in that guest. Daniel -- Daniel Veillard | Red Hat http://redhat.com/ veillard@redhat.com | libxml GNOME XML XSLT toolkit http://xmlsoft.org/ http://veillard.com/ | Rpmfind RPM search engine http://rpmfind.net/