From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from eggs.gnu.org ([2001:4830:134:3::10]:56030) by lists.gnu.org with esmtp (Exim 4.71) (envelope-from ) id 1Zw6K9-0007vo-LY for qemu-devel@nongnu.org; Tue, 10 Nov 2015 05:38:53 -0500 Received: from Debian-exim by eggs.gnu.org with spam-scanned (Exim 4.71) (envelope-from ) id 1Zw6K5-0006yW-K6 for qemu-devel@nongnu.org; Tue, 10 Nov 2015 05:38:49 -0500 Received: from mx1.redhat.com ([209.132.183.28]:60011) by eggs.gnu.org with esmtp (Exim 4.71) (envelope-from ) id 1Zw6K5-0006yS-CU for qemu-devel@nongnu.org; Tue, 10 Nov 2015 05:38:45 -0500 Received: from int-mx11.intmail.prod.int.phx2.redhat.com (int-mx11.intmail.prod.int.phx2.redhat.com [10.5.11.24]) by mx1.redhat.com (Postfix) with ESMTPS id 90FB13674CD for ; Tue, 10 Nov 2015 10:38:44 +0000 (UTC) Date: Tue, 10 Nov 2015 10:38:40 +0000 From: "Dr. David Alan Gilbert" Message-ID: <20151110103839.GB2456@work-vm> References: <1447090141-29074-1-git-send-email-quintela@redhat.com> <1447090141-29074-30-git-send-email-quintela@redhat.com> <56411C05.7080609@redhat.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <56411C05.7080609@redhat.com> Subject: Re: [Qemu-devel] [PULL 29/57] migrate_start_postcopy: Command to trigger transition to postcopy List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , To: Eric Blake Cc: amit.shah@redhat.com, Markus Armbruster , qemu-devel@nongnu.org, Juan Quintela * Eric Blake (eblake@redhat.com) wrote: > [adding Markus for a qapi question] > > On 11/09/2015 10:28 AM, Juan Quintela wrote: > > From: "Dr. David Alan Gilbert" > > > > Once postcopy is enabled (with migrate_set_capability), the migration > > will still start on precopy mode. To cause a transition into postcopy > > the: > > > > migrate_start_postcopy > > > > command must be issued. Postcopy will start sometime after this > > (when it's next checked in the migration loop). > > > > Issuing the command before migration has started will error, > > and issuing after it has finished is ignored. > > > > Signed-off-by: Dr. David Alan Gilbert > > Reviewed-by: Eric Blake > > Reviewed-by: Juan Quintela > > Reviewed-by: Amit Shah > > Signed-off-by: Juan Quintela > > --- > > I know I reviewed an earlier version of this patch, but that was > probably before 24/57 of this pull request spelled the migration > capability bit as x-postcopy-ram. It's been x-postcopy-ram since my first post, before we had migrate_set_capability ( https://lists.nongnu.org/archive/html/qemu-devel/2014-07/msg00869.html ) > > +++ b/qapi-schema.json > > @@ -702,6 +702,14 @@ > > '*tls-port': 'int', '*cert-subject': 'str' } } > > > > ## > > +# @migrate-start-postcopy > > +# > > +# Switch migration to postcopy mode > > No documentation on the relation to the [x-]postcopy-ram capability bit? docs/migration.txt does have an explanation, but I'm happy to expand this if you think it would be helpful. > Will this command always fail if that bit is not set? Yes: if (!migrate_postcopy_ram()) { error_setg(errp, "Enable postcopy with migration_set_capability before" " the start of migration"); return; } One alternative piece of text would be 'Switch current migration to postcopy mode; the x-postcopy-ram capability must be set before issuing this command.' > > +# > > +# Since: 2.5 > > +{ 'command': 'migrate-start-postcopy' } > > Should we rename this command to 'x-migrate-start-postcopy' until we are > ready to rename the entire feature to the stable namespace? If you think it's best we could; however I took the 'x-' on the capability just to be a flag to indicate it wasn't yet marked as stable; I don't think we're actually worrying about changes to naming. > If so, I'm okay with that as a followup patch (so as not to delay the > pull request), but we should really make up our minds what 2.5 will > provide on this front. Thanks, Dave > > > -- > Eric Blake eblake redhat com +1-919-301-3266 > Libvirt virtualization library http://libvirt.org > -- Dr. David Alan Gilbert / dgilbert@redhat.com / Manchester, UK