From mboxrd@z Thu Jan 1 00:00:00 1970 From: Stephen Tweedie Subject: Re: Performance on QEMU IDE disks Date: Tue, 18 Jul 2006 10:49:30 -0400 Message-ID: <20060718144930.GC32554@devserv.devel.redhat.com> References: <44B7F363.1050106@virtualiron.com> Mime-Version: 1.0 Content-Type: text/plain; charset=us-ascii Return-path: Content-Disposition: inline In-Reply-To: <44B7F363.1050106@virtualiron.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: Steve Ofsthun Cc: xen-devel@lists.xensource.com, "P M, Priya (STSD)" List-Id: xen-devel@lists.xenproject.org Hi, On Fri, Jul 14, 2006 at 03:41:23PM -0400, Steve Ofsthun wrote: > To fix this you would need to patch QEMU to used O_DIRECT when accessing > the virtual disk backing store object (block device, file, etc). We are > currently testing just such a patch for the old QEMU device model. Thanks! > I > haven't looked at the new device model to see if it already handles this. I looked last week and it still had the same problem. Note that O_DIRECT doesn't solve all of the problems either. You still end up with the _entire_ device model being blocked while the disk IO is in progress, which will leads to poor VT guest performance when trying to mix disk and CPU activity. But I'd rather have a performance problem than a data corrupter. :) --Stephen