From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from mailman by lists.gnu.org with tmda-scanned (Exim 4.43) id 1O7Dux-00043e-6K for qemu-devel@nongnu.org; Wed, 28 Apr 2010 16:31:35 -0400 Received: from [140.186.70.92] (port=44988 helo=eggs.gnu.org) by lists.gnu.org with esmtp (Exim 4.43) id 1O7Duu-0003zi-AH for qemu-devel@nongnu.org; Wed, 28 Apr 2010 16:31:34 -0400 Received: from Debian-exim by eggs.gnu.org with spam-scanned (Exim 4.69) (envelope-from ) id 1O7Dur-0001pN-8T for qemu-devel@nongnu.org; Wed, 28 Apr 2010 16:31:31 -0400 Received: from mx1.redhat.com ([209.132.183.28]:7298) by eggs.gnu.org with esmtp (Exim 4.69) (envelope-from ) id 1O7Dur-0001p0-0a for qemu-devel@nongnu.org; Wed, 28 Apr 2010 16:31:29 -0400 Date: Wed, 28 Apr 2010 17:31:19 -0300 From: Luiz Capitulino Message-ID: <20100428173119.2e9e36d8@redhat.com> In-Reply-To: <4BD874C5.2070506@codemonkey.ws> References: <1272470181-15846-1-git-send-email-kwolf@redhat.com> <1272470181-15846-2-git-send-email-kwolf@redhat.com> <4BD85BC8.50603@codemonkey.ws> <20100428140437.401d1272@redhat.com> <4BD874C5.2070506@codemonkey.ws> Mime-Version: 1.0 Content-Type: text/plain; charset=US-ASCII Content-Transfer-Encoding: 7bit Subject: [Qemu-devel] Re: [PATCH 1/2] block: Add wr_highest_sector blockstat List-Id: qemu-devel.nongnu.org List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , To: Anthony Liguori Cc: Kevin Wolf , dlaor@redhat.com, qemu-devel@nongnu.org, avi@redhat.com, danken@redhat.com On Wed, 28 Apr 2010 12:47:49 -0500 Anthony Liguori wrote: > On 04/28/2010 12:04 PM, Luiz Capitulino wrote: > > On Wed, 28 Apr 2010 11:01:12 -0500 > > Anthony Liguori wrote: > > > > > >> On 04/28/2010 10:56 AM, Kevin Wolf wrote: > >> > >>> This adds the wr_highest_sector blockstat which implements what is generally > >>> known as the high watermark. It is the highest offset of a sector written to > >>> the respective BlockDriverState since it has been opened. > >>> > >>> The query-blockstat QMP command is extended to add this value to the result, > >>> and also to add the statistics of the underlying protocol in a new "parent" > >>> field. Note that to get the "high watermark" of a qcow2 image, you need to look > >>> into the wr_highest_sector field of the parent (which can be a file, a > >>> host_device, ...). The wr_highest_sector of the qcow2 BlockDriverState itself > >>> is the highest offset on the _virtual_ disk that the guest has written to. > >>> > >>> Signed-off-by: Kevin Wolf > >>> > >>> > >> I see, you did print out stats for each layer. > >> > >> I don't think we should take 2/2. I don't mind QMP having more features > >> than the user monitor. > >> > > I don't either, but Kevin has said to me that this information is also good > > for the user Monitor. > > > > The real question here is whether or not we're going to stop supporting > > stability for the user Monitor and if so, when we'll break it. > > > > An arguable reasonable policy would be to try to maintain stability for > > existing commands. In this specific case, 'info blockstats' is used by > > libvirt afaik. So breaking it would mean that older libvirt versions won't > > be able to talk to newer qemu (taking libvirt just as real known example). > > > > I think we should try our best to maintain compatibility. In this case, > this change would break any non-QMP version of libvirt so it would be > pretty painful for users. That's why I'm inclined to not take. > > It would be reasonable to add a new info command for the user monitor if > the functionality is desirable. Seems a good solution to me too.