From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from eggs.gnu.org ([2001:4830:134:3::10]:57430) by lists.gnu.org with esmtp (Exim 4.71) (envelope-from ) id 1YYIGJ-0005cr-9R for qemu-devel@nongnu.org; Wed, 18 Mar 2015 14:00:17 -0400 Received: from Debian-exim by eggs.gnu.org with spam-scanned (Exim 4.71) (envelope-from ) id 1YYIGC-0002UH-9A for qemu-devel@nongnu.org; Wed, 18 Mar 2015 14:00:11 -0400 Received: from mx1.redhat.com ([209.132.183.28]:56484) by eggs.gnu.org with esmtp (Exim 4.71) (envelope-from ) id 1YYIGC-0002TX-1Y for qemu-devel@nongnu.org; Wed, 18 Mar 2015 14:00:04 -0400 Date: Wed, 18 Mar 2015 17:59:51 +0000 From: "Dr. David Alan Gilbert" Message-ID: <20150318175951.GL2355@work-vm> References: <1424883128-9841-1-git-send-email-dgilbert@redhat.com> <1424883128-9841-24-git-send-email-dgilbert@redhat.com> <20150313012652.GB11973@voom.redhat.com> <20150313111905.GC2486@work-vm> <20150316062355.GG5741@voom.redhat.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20150316062355.GG5741@voom.redhat.com> Subject: Re: [Qemu-devel] [PATCH v5 23/45] migrate_start_postcopy: Command to trigger transition to postcopy List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , To: David Gibson Cc: aarcange@redhat.com, yamahata@private.email.ne.jp, quintela@redhat.com, qemu-devel@nongnu.org, amit.shah@redhat.com, pbonzini@redhat.com, yanghy@cn.fujitsu.com * David Gibson (david@gibson.dropbear.id.au) wrote: > On Fri, Mar 13, 2015 at 11:19:06AM +0000, Dr. David Alan Gilbert wrote: > > * David Gibson (david@gibson.dropbear.id.au) wrote: > > > On Wed, Feb 25, 2015 at 04:51:46PM +0000, 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 > > > > --- > > > > hmp-commands.hx | 15 +++++++++++++++ > > > > hmp.c | 7 +++++++ > > > > hmp.h | 1 + > > > > include/migration/migration.h | 3 +++ > > > > migration/migration.c | 22 ++++++++++++++++++++++ > > > > qapi-schema.json | 8 ++++++++ > > > > qmp-commands.hx | 19 +++++++++++++++++++ > > > > 7 files changed, 75 insertions(+) > > > > > > > > diff --git a/hmp-commands.hx b/hmp-commands.hx > > > > index e37bc8b..03b8b78 100644 > > > > --- a/hmp-commands.hx > > > > +++ b/hmp-commands.hx > > > > @@ -985,6 +985,21 @@ Enable/Disable the usage of a capability @var{capability} for migration. > > > > ETEXI > > > > > > > > { > > > > + .name = "migrate_start_postcopy", > > > > + .args_type = "", > > > > + .params = "", > > > > + .help = "Switch migration to postcopy mode", > > > > + .mhandler.cmd = hmp_migrate_start_postcopy, > > > > + }, > > > > + > > > > +STEXI > > > > +@item migrate_start_postcopy > > > > +@findex migrate_start_postcopy > > > > +Switch in-progress migration to postcopy mode. Ignored after the end of > > > > +migration (or once already in postcopy). > > > > +ETEXI > > > > + > > > > + { > > > > .name = "client_migrate_info", > > > > .args_type = "protocol:s,hostname:s,port:i?,tls-port:i?,cert-subject:s?", > > > > .params = "protocol hostname port tls-port cert-subject", > > > > diff --git a/hmp.c b/hmp.c > > > > index b47f331..df9736c 100644 > > > > --- a/hmp.c > > > > +++ b/hmp.c > > > > @@ -1140,6 +1140,13 @@ void hmp_migrate_set_capability(Monitor *mon, const QDict *qdict) > > > > } > > > > } > > > > > > > > +void hmp_migrate_start_postcopy(Monitor *mon, const QDict *qdict) > > > > +{ > > > > + Error *err = NULL; > > > > + qmp_migrate_start_postcopy(&err); > > > > + hmp_handle_error(mon, &err); > > > > +} > > > > + > > > > void hmp_set_password(Monitor *mon, const QDict *qdict) > > > > { > > > > const char *protocol = qdict_get_str(qdict, "protocol"); > > > > diff --git a/hmp.h b/hmp.h > > > > index 4bb5dca..da1334f 100644 > > > > --- a/hmp.h > > > > +++ b/hmp.h > > > > @@ -64,6 +64,7 @@ void hmp_migrate_set_downtime(Monitor *mon, const QDict *qdict); > > > > void hmp_migrate_set_speed(Monitor *mon, const QDict *qdict); > > > > void hmp_migrate_set_capability(Monitor *mon, const QDict *qdict); > > > > void hmp_migrate_set_cache_size(Monitor *mon, const QDict *qdict); > > > > +void hmp_migrate_start_postcopy(Monitor *mon, const QDict *qdict); > > > > void hmp_set_password(Monitor *mon, const QDict *qdict); > > > > void hmp_expire_password(Monitor *mon, const QDict *qdict); > > > > void hmp_eject(Monitor *mon, const QDict *qdict); > > > > diff --git a/include/migration/migration.h b/include/migration/migration.h > > > > index e6a814a..293c83e 100644 > > > > --- a/include/migration/migration.h > > > > +++ b/include/migration/migration.h > > > > @@ -104,6 +104,9 @@ 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 a4fc7d7..43ca656 100644 > > > > --- a/migration/migration.c > > > > +++ b/migration/migration.c > > > > @@ -372,6 +372,28 @@ void qmp_migrate_set_capabilities(MigrationCapabilityStatusList *params, > > > > } > > > > } > > > > > > > > +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 == MIG_STATE_NONE) { > > > > + error_setg(errp, "Postcopy must be started after migration has been" > > > > + " started"); > > > > + return; > > > > + } > > > > + /* > > > > + * we don't error if migration has finished since that would be racy > > > > + * with issuing this command. > > > > + */ > > > > + atomic_set(&s->start_postcopy, true); > > > > > > Why atomic_set? > > > > It's being read by the migration thread, this is happening in the main thread. > > > > There's no strict ordering requirement or anything. > > I don't think you need an atomic then. AFAIK an atomic_set() in > isolation without some sort of atomic on the other side is pretty much > meaningless. The other side has an atomic_read: if (migrate_postcopy_ram() && s->state != MIGRATION_STATUS_POSTCOPY_ACTIVE && pend_nonpost <= max_size && atomic_read(&s->start_postcopy)) { if (!postcopy_start(s, &old_vm_running)) { current_active_type = MIGRATION_STATUS_POSTCOPY_ACTIVE; entered_postcopy = true; } so it is at least symmetric. Dave > > -- > David Gibson | I'll have my music baroque, and my code > david AT gibson.dropbear.id.au | minimalist, thank you. NOT _the_ _other_ > | _way_ _around_! > http://www.ozlabs.org/~dgibson -- Dr. David Alan Gilbert / dgilbert@redhat.com / Manchester, UK