From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from eggs.gnu.org ([2001:4830:134:3::10]:56814) by lists.gnu.org with esmtp (Exim 4.71) (envelope-from ) id 1VHYK7-0000nF-8O for qemu-devel@nongnu.org; Thu, 05 Sep 2013 08:06:13 -0400 Received: from Debian-exim by eggs.gnu.org with spam-scanned (Exim 4.71) (envelope-from ) id 1VHYJy-0002O2-Ea for qemu-devel@nongnu.org; Thu, 05 Sep 2013 08:06:07 -0400 Received: from nodalink.pck.nerim.net ([62.212.105.220]:60381 helo=paradis.irqsave.net) by eggs.gnu.org with esmtp (Exim 4.71) (envelope-from ) id 1VHYJy-0002NR-6d for qemu-devel@nongnu.org; Thu, 05 Sep 2013 08:05:58 -0400 Date: Thu, 5 Sep 2013 14:08:00 +0200 From: =?iso-8859-1?Q?Beno=EEt?= Canet Message-ID: <20130905120759.GA5095@irqsave.net> References: <1378215952-7151-1-git-send-email-kwolf@redhat.com> <20130905093543.GC12293@stefanha-thinkpad.redhat.com> <20130905115028.GF2826@dhcp-200-207.str.redhat.com> MIME-Version: 1.0 Content-Type: text/plain; charset=iso-8859-1 Content-Disposition: inline In-Reply-To: <20130905115028.GF2826@dhcp-200-207.str.redhat.com> Content-Transfer-Encoding: quoted-printable Subject: Re: [Qemu-devel] [RFC] qcow2 journalling draft List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , To: Kevin Wolf Cc: benoit.canet@irqsave.net, famz@redhat.com, jcody@redhat.com, qemu-devel@nongnu.org, mreitz@redhat.com, Stefan Hajnoczi > Then you get very quickly alternating sequences of "L2 depends on > refcount update" (for allocation) and "refcount update depends on L2 > update" (for freeing), which means that Qcow2Cache starts flushing all > the time without accumulating many requests. These are cases that would > benefit as well from the atomicity of journal transactions. True, Deduplication can hit this case on delete if I remember correctly and it slow down everything. Best regards Beno=EEt