From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from mailman by lists.gnu.org with tmda-scanned (Exim 4.43) id 1N7sBB-0003nz-NH for qemu-devel@nongnu.org; Tue, 10 Nov 2009 09:58:45 -0500 Received: from exim by lists.gnu.org with spam-scanned (Exim 4.43) id 1N7sB5-0003mp-Hq for qemu-devel@nongnu.org; Tue, 10 Nov 2009 09:58:44 -0500 Received: from [199.232.76.173] (port=50831 helo=monty-python.gnu.org) by lists.gnu.org with esmtp (Exim 4.43) id 1N7sB5-0003mf-A7 for qemu-devel@nongnu.org; Tue, 10 Nov 2009 09:58:39 -0500 Received: from e4.ny.us.ibm.com ([32.97.182.144]:45009) by monty-python.gnu.org with esmtps (TLS-1.0:DHE_RSA_AES_256_CBC_SHA1:32) (Exim 4.60) (envelope-from ) id 1N7sB4-0004KD-Ts for qemu-devel@nongnu.org; Tue, 10 Nov 2009 09:58:39 -0500 Received: from d01relay06.pok.ibm.com (d01relay06.pok.ibm.com [9.56.227.116]) by e4.ny.us.ibm.com (8.14.3/8.13.1) with ESMTP id nAAEoPbj019329 for ; Tue, 10 Nov 2009 09:50:25 -0500 Received: from d01av01.pok.ibm.com (d01av01.pok.ibm.com [9.56.224.215]) by d01relay06.pok.ibm.com (8.13.8/8.13.8/NCO v10.0) with ESMTP id nAAEwVHH794784 for ; Tue, 10 Nov 2009 09:58:31 -0500 Received: from d01av01.pok.ibm.com (loopback [127.0.0.1]) by d01av01.pok.ibm.com (8.14.3/8.13.1/NCO v10.0 AVout) with ESMTP id nAAEwVF4014684 for ; Tue, 10 Nov 2009 09:58:31 -0500 Message-ID: <4AF97F93.2080707@us.ibm.com> Date: Tue, 10 Nov 2009 08:58:27 -0600 From: Anthony Liguori MIME-Version: 1.0 Subject: Re: [Qemu-devel] Re: virtio: Add memory statistics reporting to the balloon driver References: <1257782838.2835.5.camel@aglitke> <1257784326.2835.16.camel@aglitke> <200911101312.02650.rusty@rustcorp.com.au> <4AF97A5E.1070801@codemonkey.ws> <4AF97C1A.2080609@redhat.com> In-Reply-To: <4AF97C1A.2080609@redhat.com> Content-Type: text/plain; charset=UTF-8; format=flowed Content-Transfer-Encoding: 7bit List-Id: qemu-devel.nongnu.org List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , To: Avi Kivity Cc: agl@linux.vnet.ibm.com, Rusty Russell , qemu-devel@nongnu.org, linux-kernel@vger.kernel.org, virtualization@lists.linux-foundation.org Avi Kivity wrote: > On 11/10/2009 04:36 PM, Anthony Liguori wrote: >> >>> A stats vq might solve this more cleanly? >> >> actual and target are both really just stats. Had we implemented >> those with a vq, I'd be inclined to agree with you but since they're >> implemented in the config space, it seems natural to extend the >> config space with other stats. >> > > There is in fact a difference; actual and target are very rarely > updated, while the stats are updated very often. Using a vq means a > constant number of exits per batch instead of one exit per statistic. > If the vq is host-driven, it also allows the host to control the > update frequency dynamically (i.e. stop polling when there is no > memory pressure). I'm not terribly opposed to using a vq for this. I would expect the stat update interval to be rather long (10s probably) but a vq works just as well. -- Regards, Anthony Liguori