From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from eggs.gnu.org ([2001:4830:134:3::10]:37647) by lists.gnu.org with esmtp (Exim 4.71) (envelope-from ) id 1dAJIK-0006aK-SA for qemu-devel@nongnu.org; Mon, 15 May 2017 12:56:29 -0400 Received: from Debian-exim by eggs.gnu.org with spam-scanned (Exim 4.71) (envelope-from ) id 1dAJIF-0007T9-RT for qemu-devel@nongnu.org; Mon, 15 May 2017 12:56:28 -0400 Received: from mx1.redhat.com ([209.132.183.28]:45948) by eggs.gnu.org with esmtps (TLS1.0:DHE_RSA_AES_256_CBC_SHA1:32) (Exim 4.71) (envelope-from ) id 1dAJIF-0007Sb-Ir for qemu-devel@nongnu.org; Mon, 15 May 2017 12:56:23 -0400 Received: from smtp.corp.redhat.com (int-mx03.intmail.prod.int.phx2.redhat.com [10.5.11.13]) (using TLSv1.2 with cipher AECDH-AES256-SHA (256/256 bits)) (No client certificate requested) by mx1.redhat.com (Postfix) with ESMTPS id 3C058C04B92C for ; Mon, 15 May 2017 16:56:22 +0000 (UTC) From: Juan Quintela In-Reply-To: <20170515163841.GB2324@work-vm> (David Alan Gilbert's message of "Mon, 15 May 2017 17:38:41 +0100") References: <20170511163228.6666-1-quintela@redhat.com> <20170511163228.6666-3-quintela@redhat.com> <20170512034033.GN28293@pxdev.xzpeter.org> <877f1mgx9h.fsf@secure.mitica> <5bab598f-30eb-fcf6-9d06-8f683b466414@redhat.com> <87lgpyfo28.fsf@secure.mitica> <87k25iqf4m.fsf@dusky.pond.sub.org> <87efvqdqqj.fsf@secure.mitica> <20170515163841.GB2324@work-vm> Reply-To: quintela@redhat.com Date: Mon, 15 May 2017 18:56:18 +0200 Message-ID: <87a86edpot.fsf@secure.mitica> MIME-Version: 1.0 Content-Type: text/plain Subject: Re: [Qemu-devel] [PATCH 2/3] migration: Remove use of old MigrationParams List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , To: "Dr. David Alan Gilbert" Cc: Markus Armbruster , Eric Blake , lvivier@redhat.com, qemu-devel@nongnu.org, Peter Xu "Dr. David Alan Gilbert" wrote: > * Juan Quintela (quintela@redhat.com) wrote: >> Markus Armbruster wrote: >> > Juan Quintela writes: >> > >> >> Eric Blake wrote: >> >> >> >>> Or is the proposal that we are also going to simplify the QMP 'migrate' >> >>> command to get rid of crufty parameters? >> >> >> >> I didn't read it that way, but I would not oppose O:-) >> >> >> >> Later, Juan. >> > >> > I'm not too familiar with this stuff, so please correct my >> > misunderstandings. >> > >> > "Normal" migration configuration is global state, i.e. it applies to all >> > future migrations. >> > >> > Except the "migrate" command's flags apply to just the migration kicked >> > off by that command. >> > >> > QMP command "migrate" has two flags "blk" (HMP: -b) and "inc" (HMP: -i). >> > !blk && inc makes no sense and is silently treated like !blk && !inc. >> > >> > There's a third flag "detach" (HMP: -d), but it does nothing in QMP. >> >> As qmp command is asynchronous, you can think that -d is *always* on in >> QMP O:-) >> >> > You'd like to deprecate these flags in favour of "normal" configuration. >> > However, we need to maintain QMP backward compatibility at least for a >> > while. HMP backward compatibility is nice to have, but not required. >> > >> > First step is to design the new interface you want. Second step is to >> > figure out backward compatibility. >> > >> > The new interface adds a block migration tri-state (off, >> > non-incremental, incremental) to global state, default off. Whether >> > it's done as two bools or an enum of three values doesn't matter here. >> >> Tristates will complicate it. I still think that: >> >> - capability: block_migration >> - parameter: block_shared >> >> Makes more sense, no? > > I don't understand what making block_shared a parameter gives you as > opposed to simply having two capabilities. > > (And how did we get 'shared'? We started off with block & incremental) The variables on MigrationParams: struct MigrationParams { bool blk; bool shared; }; I can move to incremental. I am not sure which one is clearer. The advantage of having shared as a parameter is that we forget about all this dependency bussiness. Is the same than compression_threads paramter, you setup to whichever value that you want. But you don't get compression_threads until you set the compress capability. So, in this case we will have: block capability: Are we using block migration or not block-incremental parameter: If we are using block migration, are we using incremental copying of the block layer? Later, Juan.