From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from eggs.gnu.org ([2001:4830:134:3::10]:59069) by lists.gnu.org with esmtp (Exim 4.71) (envelope-from ) id 1Zf7No-0003h2-Ip for qemu-devel@nongnu.org; Thu, 24 Sep 2015 10:20:28 -0400 Received: from Debian-exim by eggs.gnu.org with spam-scanned (Exim 4.71) (envelope-from ) id 1Zf7Ni-00036z-2f for qemu-devel@nongnu.org; Thu, 24 Sep 2015 10:20:24 -0400 Received: from mx1.redhat.com ([209.132.183.28]:39448) by eggs.gnu.org with esmtp (Exim 4.71) (envelope-from ) id 1Zf7Nh-00036r-R4 for qemu-devel@nongnu.org; Thu, 24 Sep 2015 10:20:17 -0400 Date: Thu, 24 Sep 2015 15:20:11 +0100 From: "Dr. David Alan Gilbert" Message-ID: <20150924142010.GC2552@work-vm> References: <1434450415-11339-1-git-send-email-dgilbert@redhat.com> <1434450415-11339-23-git-send-email-dgilbert@redhat.com> <87380sl2rx.fsf@neno.neno> <20150713171340.GK2492@work-vm> <87mvz0hqx3.fsf@neno.neno> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <87mvz0hqx3.fsf@neno.neno> Subject: Re: [Qemu-devel] [PATCH v7 22/42] migrate_start_postcopy: Command to trigger transition to postcopy List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , To: Juan Quintela Cc: aarcange@redhat.com, yamahata@private.email.ne.jp, liang.z.li@intel.com, qemu-devel@nongnu.org, luis@cs.umu.se, amit.shah@redhat.com, pbonzini@redhat.com, david@gibson.dropbear.id.au * Juan Quintela (quintela@redhat.com) wrote: > "Dr. David Alan Gilbert" wrote: > > * Juan Quintela (quintela@redhat.com) wrote: > >> "Dr. David Alan Gilbert (git)" 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 > >> > >> > diff --git a/include/migration/migration.h b/include/migration/migration.h > >> > index a5951ac..e973490 100644 > >> > --- a/include/migration/migration.h > >> > +++ b/include/migration/migration.h > >> > @@ -111,6 +111,9 @@ struct MigrationState > >> > int64_t xbzrle_cache_size; > >> > int64_t setup_time; > >> > int64_t dirty_sync_count; > >> > + > >> > + /* Flag set once the migration has been asked to enter postcopy */ > >> > + bool start_postcopy; > >> > }; > >> > > >> > void process_incoming_migration(QEMUFile *f); > >> > diff --git a/migration/migration.c b/migration/migration.c > >> > index e77b8b4..6fc47f9 100644 > >> > --- a/migration/migration.c > >> > +++ b/migration/migration.c > >> > @@ -465,6 +465,28 @@ void qmp_migrate_set_parameters(bool has_compress_level, > >> > } > >> > } > >> > > >> > +void qmp_migrate_start_postcopy(Error **errp) > >> > +{ > >> > + MigrationState *s = migrate_get_current(); > >> > + > >> > + if (!migrate_postcopy_ram()) { > >> > + error_setg(errp, "Enable postcopy with migration_set_capability before" > >> > + " the start of migration"); > >> > + return; > >> > + } > >> > + > >> > + if (s->state == MIGRATION_STATUS_NONE) { > >> > >> I would claim that this check should be: > >> > >> if (s->state != MIGRATION_STATUS_ACTIVE) { > >> ?? > >> > >> FAILED, COMPLETED, CANCELL* don't make sense, right? > > > > What I'm trying to catch here is people doing: > > migrate_start_postcopy > > migrate tcp:pppp:whereever > > > > which wont work, because migrate_init reinitialises > > the flag that start previously set. > > > > However, I also don't want to create a race, since what you do is > > typically: > > migrate tcp:pppp:whereever > > > > migrate_start_postcopy > > > > if you're unlucky, and the migration finishes just > > at the same time you do the migrate_start_postcopy, do you > > want migrate_start_postcopy to fail? My guess was it > > was best for it not to fail, in this case. > > Change the order, if it is ACTIVE: do the postcopy thing, otherwise, do > the clause that is protected now? Moving to postcopy only make sense if > we are in active. The problem is that produces a race-condition for the command. If you wait too long and the migration finishes before you issue the command you get an error, when the migration has completed perfectly happily. Dave > > Later, Juan. > > > > > > Dave > > > >> > >> Thanks, Juan. > > -- > > Dr. David Alan Gilbert / dgilbert@redhat.com / Manchester, UK -- Dr. David Alan Gilbert / dgilbert@redhat.com / Manchester, UK