From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from [140.186.70.92] (port=45149 helo=eggs.gnu.org) by lists.gnu.org with esmtp (Exim 4.43) id 1OnrLF-0005nO-64 for qemu-devel@nongnu.org; Tue, 24 Aug 2010 07:06:58 -0400 Received: from Debian-exim by eggs.gnu.org with spam-scanned (Exim 4.69) (envelope-from ) id 1OnrLD-0005ub-Vt for qemu-devel@nongnu.org; Tue, 24 Aug 2010 07:06:56 -0400 Received: from isrv.corpit.ru ([86.62.121.231]:42871) by eggs.gnu.org with esmtp (Exim 4.69) (envelope-from ) id 1OnrLD-0005u7-OX for qemu-devel@nongnu.org; Tue, 24 Aug 2010 07:06:55 -0400 Message-ID: <4C73A7CB.5000707@msgid.tls.msk.ru> Date: Tue, 24 Aug 2010 15:06:51 +0400 From: Michael Tokarev MIME-Version: 1.0 References: <1282646430-5777-1-git-send-email-kwolf@redhat.com> In-Reply-To: Content-Type: text/plain; charset=ISO-8859-1 Content-Transfer-Encoding: 7bit Subject: [Qemu-devel] Re: [RFC][STABLE 0.13] Revert "qcow2: Use bdrv_(p)write_sync for metadata writes" List-Id: qemu-devel.nongnu.org List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , To: Stefan Hajnoczi Cc: Kevin Wolf , avi@redhat.com, qemu-devel@nongnu.org, hch@lst.de 24.08.2010 15:02, Stefan Hajnoczi wrote: [] > Sometimes an improvement has a side effect and it makes sense to hold > back the improvement until the side effect can be resolved. The > period of time in which users could rely on qcow2 data integrity is > small to none, I feel reverting the commit makes sense. And I agree with this. > QEMU 0.12.5 has qcow2 sync metadata writes in commit > 37060c28e522843fbf6f7e59af745dfcb05b132c. Was the performance > regression spotted on 0.12.5 or 0.13? It started as a debian bugreport ( http://bugs.debian.org/594069 ) which were reported once 0.12.5 entered debian testing. So it were spotted in 0.12.5, not 0.13. I verfied the bug locally and indeed, it makes _huge_ difference (0.12.4 vs 0.12.5), -- e.g 600mb mem windows7 hybernation on my machine now takes about 40 minutes to complete instead of ~20 sec in 0.12.4. I'm reverting whole series (there are 5 patches in total, covering qcow, qcow2, vmdk and vpc plus infrastructure) for debian 0.12 package. It is sad but there's no other option for now. /mjt