From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from mailman by lists.gnu.org with tmda-scanned (Exim 4.43) id 1G6ZSM-00074v-Au for qemu-devel@nongnu.org; Fri, 28 Jul 2006 17:01:14 -0400 Received: from exim by lists.gnu.org with spam-scanned (Exim 4.43) id 1G6ZSL-00074O-Eg for qemu-devel@nongnu.org; Fri, 28 Jul 2006 17:01:13 -0400 Received: from [199.232.76.173] (helo=monty-python.gnu.org) by lists.gnu.org with esmtp (Exim 4.43) id 1G6ZSL-00074I-BA for qemu-devel@nongnu.org; Fri, 28 Jul 2006 17:01:13 -0400 Received: from [65.74.133.4] (helo=mail.codesourcery.com) by monty-python.gnu.org with esmtps (TLS-1.0:DHE_RSA_AES_256_CBC_SHA:32) (Exim 4.52) id 1G6ZUP-0003Tk-4K for qemu-devel@nongnu.org; Fri, 28 Jul 2006 17:03:21 -0400 From: Paul Brook Subject: Re: [Qemu-devel] Re: [RFC][PATCH] make sure disk writes actually hit disk Date: Fri, 28 Jul 2006 22:01:08 +0100 References: <44CA6B76.7000004@redhat.com> <200607282130.11255.paul@codesourcery.com> <44CA76E6.4050702@redhat.com> In-Reply-To: <44CA76E6.4050702@redhat.com> MIME-Version: 1.0 Content-Type: text/plain; charset="utf-8" Content-Transfer-Encoding: 7bit Content-Disposition: inline Message-Id: <200607282201.09092.paul@codesourcery.com> Reply-To: qemu-devel@nongnu.org List-Id: qemu-devel.nongnu.org List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , To: Rik van Riel Cc: alan@redhat.com, qemu-devel@nongnu.org > > Have you measured the impact of O_SYNC? I wouldn't be surprised if it was > > significant. > > I suspect it'll be horrific in the qemu codebase (blocking execution > of the guest OS until disk IO is complete), but it's fine in the Xen > qemu-dm situation, where IO completion happens asynchronously. > > The recent commit message on the Xen side did not suggest there was > that much of a difference between both qemu code bases. Obviously > I was wrong, and the O_SYNC bandaid should probably be kept out for > now. Ah, ok. I didn't realise they'd diverged that much either. Paul