From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from eggs.gnu.org ([2001:4830:134:3::10]:56098) by lists.gnu.org with esmtp (Exim 4.71) (envelope-from ) id 1aYFDM-0003K7-V9 for qemu-devel@nongnu.org; Tue, 23 Feb 2016 10:49:29 -0500 Received: from Debian-exim by eggs.gnu.org with spam-scanned (Exim 4.71) (envelope-from ) id 1aYFDI-00078n-Ey for qemu-devel@nongnu.org; Tue, 23 Feb 2016 10:49:28 -0500 Received: from mx1.redhat.com ([209.132.183.28]:55175) by eggs.gnu.org with esmtp (Exim 4.71) (envelope-from ) id 1aYFDI-00078j-A1 for qemu-devel@nongnu.org; Tue, 23 Feb 2016 10:49:24 -0500 Date: Tue, 23 Feb 2016 17:49:21 +0200 From: "Michael S. Tsirkin" Message-ID: <20160223174837-mutt-send-email-mst@redhat.com> References: <1456239585-13324-1-git-send-email-den@openvz.org> <1456239585-13324-2-git-send-email-den@openvz.org> <20160223172048-mutt-send-email-mst@redhat.com> <56CC7ADD.5080508@openvz.org> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <56CC7ADD.5080508@openvz.org> Subject: Re: [Qemu-devel] [PATCH 1/2] virtio-balloon: export all balloon statistics List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , To: "Denis V. Lunev" Cc: Igor Redko , qemu-devel@nongnu.org On Tue, Feb 23, 2016 at 06:29:33PM +0300, Denis V. Lunev wrote: > On 02/23/2016 06:24 PM, Michael S. Tsirkin wrote: > >On Tue, Feb 23, 2016 at 05:59:44PM +0300, Denis V. Lunev wrote: > >>From: Igor Redko > >> > >>We are making experiments with different autoballooning strategies > >>based on the guest behavior. Thus we need to experiment with different > >>guest statistics. For now every counter change requires QEMU recompilation > >>and dances with Libvirt. > >> > >>This patch introduces transport for unrecognized counters in virtio-balloon. > >>This transport can be used for measuring benefits from using new > >>balloon counters, before submitting any patches. Current alternative > >>is 'guest-exec' transport which isn't made for such delicate matters > >>and can influence test results. > >> > >>Originally all counters with tag >= VIRTIO_BALLOON_S_NR were ignored. > >>Instead of this we keep first (VIRTIO_BALLOON_S_NR + 32) counters from the > >>queue and pass unrecognized ones with the following names: 'x-stat-XXXX', > >>where XXXX is a tag number in hex. Defined counters are reported with their > >>regular names. > >> > >>Signed-off-by: Igor Redko > >>Signed-off-by: Denis V. Lunev > >>CC: Michael S. Tsirkin > >This seems to open the ABI to abuse. > >Seems like a reasonable way to experiment though. > >How about adding this within #if 0 statements? > >You can uncomment them for debugging ... > I'd prefer to have this enabled. > > Why do you think that it opens "abuse" way? Because people will use this to hack drivers and management tools bypassing qemu. > Actually the amount of host data is limited. If the guest > will send fake stats before real ones - this guest is > not cooperative and in this case the guest can > hust ignore any balloon change requests.