From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from eggs.gnu.org ([2001:4830:134:3::10]:38691) by lists.gnu.org with esmtp (Exim 4.71) (envelope-from ) id 1Z0s6D-0003O5-LF for qemu-devel@nongnu.org; Fri, 05 Jun 2015 09:55:54 -0400 Received: from Debian-exim by eggs.gnu.org with spam-scanned (Exim 4.71) (envelope-from ) id 1Z0s69-0006V4-DR for qemu-devel@nongnu.org; Fri, 05 Jun 2015 09:55:53 -0400 From: Alberto Garcia In-Reply-To: <556F0CC5.4040401@redhat.com> References: <20150603134042.GA22770@igalia.com> <556F0CC5.4040401@redhat.com> Date: Fri, 05 Jun 2015 15:55:46 +0200 Message-ID: MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Subject: Re: [Qemu-devel] I/O accounting overhaul List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , To: Eric Blake , qemu-devel@nongnu.org Cc: Kevin Wolf , Markus Armbruster , Stefan Hajnoczi , qemu-block@nongnu.org, Max Reitz On Wed 03 Jun 2015 04:18:45 PM CEST, Eric Blake wrote: >> The accounting stats are stored in the BlockDriverState, but they're >> actually from the device backed by the BDS, so they could probably be >> moved there. For the interface we could extend BlockDeviceStats and >> add the new fields, but query-blockstats works on BDS, so maybe we >> need new API? > > We want stats per BDS (it would be nice to know how many reads are > satisfied from the active layer, vs. how many are satisfied from the > backing image, to know how stable and useful the backing image is). > But we also want stats per BB (how many reads did the guest attempt, > regardless of which BDS served the read). So any good solution needs > to work from both views (whether by two API, or by one with a flag, is > bike-shedding). That's right. As I said my priority is the stats from the BB (i.e. what the guest can see), but I agree that any solution has to consider that we want to have both eventually. Berto