From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from mailman by lists.gnu.org with tmda-scanned (Exim 4.43) id 1O6gav-0002a7-Je for qemu-devel@nongnu.org; Tue, 27 Apr 2010 04:56:41 -0400 Received: from [140.186.70.92] (port=42893 helo=eggs.gnu.org) by lists.gnu.org with esmtp (Exim 4.43) id 1O6gar-0002Yh-Th for qemu-devel@nongnu.org; Tue, 27 Apr 2010 04:56:41 -0400 Received: from Debian-exim by eggs.gnu.org with spam-scanned (Exim 4.69) (envelope-from ) id 1O6gak-0006p2-Fv for qemu-devel@nongnu.org; Tue, 27 Apr 2010 04:56:37 -0400 Received: from mx1.redhat.com ([209.132.183.28]:38775) by eggs.gnu.org with esmtp (Exim 4.69) (envelope-from ) id 1O6gak-0006oo-8j for qemu-devel@nongnu.org; Tue, 27 Apr 2010 04:56:30 -0400 Message-ID: <4BD6A6BA.1090600@redhat.com> Date: Tue, 27 Apr 2010 11:56:26 +0300 From: Avi Kivity MIME-Version: 1.0 References: <20100426172634.GC15278@x200.localdomain> <4BD5D28C.7080700@codemonkey.ws> <20100426221258.GH15278@x200.localdomain> <4BD61584.9080208@codemonkey.ws> <4BD69D03.2050502@redhat.com> <4BD6A4CA.6070306@redhat.com> In-Reply-To: <4BD6A4CA.6070306@redhat.com> Content-Type: text/plain; charset=UTF-8; format=flowed Content-Transfer-Encoding: 7bit Subject: [Qemu-devel] Re: KVM call agenda for Apr 27 List-Id: qemu-devel.nongnu.org List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , To: dlaor@redhat.com Cc: Chris Wright , Kevin Wolf , kvm@vger.kernel.org, qemu-devel@nongnu.org On 04/27/2010 11:48 AM, Dor Laor wrote: >> Here's another option: an nbd-like protocol that remotes all BlockDriver >> operations except read and write over a unix domain socket. The open >> operation returns an fd (SCM_RIGHTS strikes again) that is used for read >> and write. This can be used to implement snapshots over LVM, for >> example. >> > > > Why w/o read/writes? To avoid the copying. > the watermark code needs them too (as info, not the actual buffer). Yeah. It works for lvm snapshots, not for watermarks. > > IMHO the whole thing is way over engineered: > a) Having another channel into qemu is complicating management > software. Isn't the monitor should be the channel? Otherwise we'll > need to create another QMP (or nbd like Avi suggest) for these > actions. It's extra work for mgmt and they will have hard time to > understand events interleaving of the various channels block layer plugins allow intercepting all interesting block layer events, not just write-past-a-watermark, and allow actions based on those events. It's a more general solution. > b) How the plugins are defined? Is it scripts? Binaries? Do they open > their own sockets? Shared objects. -- error compiling committee.c: too many arguments to function