From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from mailman by lists.gnu.org with tmda-scanned (Exim 4.43) id 1O7BMc-0006Xa-Ae for qemu-devel@nongnu.org; Wed, 28 Apr 2010 13:47:58 -0400 Received: from [140.186.70.92] (port=52981 helo=eggs.gnu.org) by lists.gnu.org with esmtp (Exim 4.43) id 1O7BMa-0006W2-SS for qemu-devel@nongnu.org; Wed, 28 Apr 2010 13:47:57 -0400 Received: from Debian-exim by eggs.gnu.org with spam-scanned (Exim 4.69) (envelope-from ) id 1O7BMY-0006SS-Rx for qemu-devel@nongnu.org; Wed, 28 Apr 2010 13:47:56 -0400 Received: from mail-px0-f173.google.com ([209.85.212.173]:37192) by eggs.gnu.org with esmtp (Exim 4.69) (envelope-from ) id 1O7BMY-0006SH-NL for qemu-devel@nongnu.org; Wed, 28 Apr 2010 13:47:54 -0400 Received: by pxi19 with SMTP id 19so2594904pxi.4 for ; Wed, 28 Apr 2010 10:47:53 -0700 (PDT) Message-ID: <4BD874C5.2070506@codemonkey.ws> Date: Wed, 28 Apr 2010 12:47:49 -0500 From: Anthony Liguori MIME-Version: 1.0 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> In-Reply-To: <20100428140437.401d1272@redhat.com> Content-Type: text/plain; charset=ISO-8859-1; format=flowed 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: Luiz Capitulino Cc: Kevin Wolf , dlaor@redhat.com, qemu-devel@nongnu.org, avi@redhat.com, danken@redhat.com 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. Regards, Anthony Liguori