From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from eggs.gnu.org ([2001:4830:134:3::10]:39376) by lists.gnu.org with esmtp (Exim 4.71) (envelope-from ) id 1aUosC-0008GB-6c for qemu-devel@nongnu.org; Sun, 14 Feb 2016 00:05:28 -0500 Received: from Debian-exim by eggs.gnu.org with spam-scanned (Exim 4.71) (envelope-from ) id 1aUos9-0005Sg-01 for qemu-devel@nongnu.org; Sun, 14 Feb 2016 00:05:28 -0500 Received: from mx1.redhat.com ([209.132.183.28]:33584) by eggs.gnu.org with esmtp (Exim 4.71) (envelope-from ) id 1aUos8-0005Sb-R6 for qemu-devel@nongnu.org; Sun, 14 Feb 2016 00:05:24 -0500 Date: Sun, 14 Feb 2016 13:05:20 +0800 From: Fam Zheng Message-ID: <20160214050520.GA9723@ad.usersys.redhat.com> References: <1454151394-52320-1-git-send-email-vsementsov@virtuozzo.com> <1454151394-52320-3-git-send-email-vsementsov@virtuozzo.com> <20160210100825.GA7317@stefanha-x1.localdomain> <56BB41AE.8090609@virtuozzo.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <56BB41AE.8090609@virtuozzo.com> Subject: Re: [Qemu-devel] [PATCH 2/6] qmp: add query-block-dirty-bitmap-ranges List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , To: "Denis V. Lunev" Cc: kwolf@redhat.com, Vladimir Sementsov-Ogievskiy , Stefan Hajnoczi , qemu-devel@nongnu.org, armbru@redhat.com, jsnow@redhat.com On Wed, 02/10 16:57, Denis V. Lunev wrote: > On 02/10/2016 01:08 PM, Stefan Hajnoczi wrote: > >On Sat, Jan 30, 2016 at 01:56:30PM +0300, Vladimir Sementsov-Ogievskiy wrote: > >>Add qmp command to query dirty bitmap contents. This is needed for > >>external backup. > >> > >>Signed-off-by: Vladimir Sementsov-Ogievskiy > >>--- > >> block/dirty-bitmap.c | 55 +++++++++++++++++++++++++++++++++++++++ > >> blockdev.c | 62 ++++++++++++++++++++++++++++++++++++++++++++ > >> include/block/dirty-bitmap.h | 7 +++++ > >> qapi/block-core.json | 54 ++++++++++++++++++++++++++++++++++++++ > >> qmp-commands.hx | 33 +++++++++++++++++++++++ > >> 5 files changed, 211 insertions(+) > >This API produces large replies and/or requires many calls to fetch all > >bitmap data. The worst case is a 101010... bitmap. > > > >I consider the dirty bitmap to be data (vs control) and not something > >that should be sent over a control channel like the QMP monitor. > > > >How about writing the dirty bitmap to a file? The new bitmap file > >format that Fam is working on could be used. That way the dirty bitmap > >can be saved asynchronously without hogging the QMP monitor. > Reasonable point. > > May be it would be better to setup "special" NBD server inside > QEMU which will allow to directly "read" bitmap data. > > Any opinion? Since Stefan has mentioned "the format" I'm working on, yes, I think it will be possible to expose the persistent bitmap through NBD if the driver assigns node-names to the bitmap BDS. Let me prototype this on top of my branch. Fam