From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from eggs.gnu.org ([208.118.235.92]:55273) by lists.gnu.org with esmtp (Exim 4.71) (envelope-from ) id 1TlHoQ-0003Jy-4q for qemu-devel@nongnu.org; Wed, 19 Dec 2012 06:27:47 -0500 Received: from Debian-exim by eggs.gnu.org with spam-scanned (Exim 4.71) (envelope-from ) id 1TlHoP-00039K-12 for qemu-devel@nongnu.org; Wed, 19 Dec 2012 06:27:46 -0500 Received: from mx1.redhat.com ([209.132.183.28]:37413) by eggs.gnu.org with esmtp (Exim 4.71) (envelope-from ) id 1TlHoO-00039G-PZ for qemu-devel@nongnu.org; Wed, 19 Dec 2012 06:27:44 -0500 Date: Wed, 19 Dec 2012 09:27:41 -0200 From: Luiz Capitulino Message-ID: <20121219092741.564abff5@doriath.home> In-Reply-To: <50D0E158.9070004@redhat.com> References: <1355500182-12743-1-git-send-email-lcapitulino@redhat.com> <1355500182-12743-2-git-send-email-lcapitulino@redhat.com> <24E144B8C0207547AD09C467A8259F75578B48B1@lisa.maurer-it.com> <50D0E158.9070004@redhat.com> Mime-Version: 1.0 Content-Type: text/plain; charset=US-ASCII Content-Transfer-Encoding: 7bit Subject: Re: [Qemu-devel] [PATCH 1/3] balloon: drop old stats code & API List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , To: Eric Blake Cc: "mdroth@linux.vnet.ibm.com" , "aliguori@us.ibm.com" , "agl@us.ibm.com" , Dietmar Maurer , "qemu-devel@nongnu.org" On Tue, 18 Dec 2012 14:34:16 -0700 Eric Blake wrote: > On 12/17/2012 03:13 AM, Dietmar Maurer wrote: > >> Next commit will re-enable balloon stats with a different interface, but this > >> old code conflicts with it. Let's drop it. > > > > I don't really see any conflicts here? > > > >> It's important to note that the QMP and HMP interfaces are also dropped by > >> this commit. That shouldn't be a problem though, because: > >> > >> 1. All QMP fields are optional > >> 2. This has never been really used > > Libvirt has been using it when available (although reluctantly, as it > risks hanging on an uncooperative guest); This has always been disabled and qemu never returns the stats info. I believe libvirt's code is rotting just like qemu's is. > and while libvirt can be > patched to call 6 QOM commands in a row to query six different QOM > stats, I still think it would be nicer to add a command that provides > all the stats at once. In particular, when calling 6 commands in > series, you no longer have an atomic picture of the guest (the polling > interval could hit between two QOM queries, resulting in a combined set > of statistics that has no counterpart to the transition of states that > the guest actually went through). On the other hand, since the stats > are already polling-based, and since it requires cooperation from the > guest, not having a guarantee of an atomic set of stats is not really > much of a loss. Something I have been wondering if whether it's possible to have only one property (say balloon-statistics) and return all properties in a dict. QOM properties return a visitor, so maybe that's possible. I'll check that.