From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from eggs.gnu.org ([2001:4830:134:3::10]:52149) by lists.gnu.org with esmtp (Exim 4.71) (envelope-from ) id 1ddYLK-0004na-GU for qemu-devel@nongnu.org; Fri, 04 Aug 2017 04:52:27 -0400 Received: from Debian-exim by eggs.gnu.org with spam-scanned (Exim 4.71) (envelope-from ) id 1ddYLG-00046y-UV for qemu-devel@nongnu.org; Fri, 04 Aug 2017 04:52:26 -0400 Received: from mx1.redhat.com ([209.132.183.28]:37762) by eggs.gnu.org with esmtps (TLS1.0:DHE_RSA_AES_256_CBC_SHA1:32) (Exim 4.71) (envelope-from ) id 1ddYLG-00046L-KZ for qemu-devel@nongnu.org; Fri, 04 Aug 2017 04:52:22 -0400 Date: Fri, 4 Aug 2017 16:52:16 +0800 From: Peter Xu Message-ID: <20170804085216.GO5561@pxdev.xzpeter.org> References: <1501229198-30588-1-git-send-email-peterx@redhat.com> <1501229198-30588-30-git-send-email-peterx@redhat.com> <20170803135434.GB3673@work-vm> MIME-Version: 1.0 Content-Type: text/plain; charset=utf-8 Content-Disposition: inline In-Reply-To: <20170803135434.GB3673@work-vm> Subject: Re: [Qemu-devel] [RFC 29/29] migration: reset migrate thread vars when resumed List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , To: "Dr. David Alan Gilbert" Cc: qemu-devel@nongnu.org, Laurent Vivier , Alexey Perevalov , Juan Quintela , Andrea Arcangeli On Thu, Aug 03, 2017 at 02:54:35PM +0100, Dr. David Alan Gilbert wrote: > * Peter Xu (peterx@redhat.com) wrote: > > Firstly, MigThrError enumeration is introduced to describe the error in > > migration_detect_error() better. This gives the migration_thread() a > > chance to know whether a recovery has happened. > > > > Then, if a recovery is detected, migration_thread() will reset its local > > variables to prepare for that. > > > > Signed-off-by: Peter Xu > > --- > > migration/migration.c | 40 +++++++++++++++++++++++++++++----------- > > 1 file changed, 29 insertions(+), 11 deletions(-) > > > > diff --git a/migration/migration.c b/migration/migration.c > > index ecebe30..439bc22 100644 > > --- a/migration/migration.c > > +++ b/migration/migration.c > > @@ -2159,6 +2159,15 @@ static bool postcopy_should_start(MigrationState *s) > > return atomic_read(&s->start_postcopy) || s->start_postcopy_fast; > > } > > > > +typedef enum MigThrError { > > + /* No error detected */ > > + MIG_THR_ERR_NONE = 0, > > + /* Detected error, but resumed successfully */ > > + MIG_THR_ERR_RECOVERED = 1, > > + /* Detected fatal error, need to exit */ > > + MIG_THR_ERR_FATAL = 2, > > +} MigThrError; > > + > > Could you move this patch earlier to when postcopy_pause is created > so it's created with this enum? Sure. [...] > > @@ -2319,6 +2327,7 @@ static void *migration_thread(void *opaque) > > /* The active state we expect to be in; ACTIVE or POSTCOPY_ACTIVE */ > > enum MigrationStatus current_active_state = MIGRATION_STATUS_ACTIVE; > > bool enable_colo = migrate_colo_enabled(); > > + MigThrError thr_error; > > > > rcu_register_thread(); > > > > @@ -2395,8 +2404,17 @@ static void *migration_thread(void *opaque) > > * Try to detect any kind of failures, and see whether we > > * should stop the migration now. > > */ > > - if (migration_detect_error(s)) { > > + thr_error = migration_detect_error(s); > > + if (thr_error == MIG_THR_ERR_FATAL) { > > + /* Stop migration */ > > break; > > + } else if (thr_error == MIG_THR_ERR_RECOVERED) { > > + /* > > + * Just recovered from a e.g. network failure, reset all > > + * the local variables. > > + */ > > + initial_time = qemu_clock_get_ms(QEMU_CLOCK_REALTIME); > > + initial_bytes = 0; > > They don't seem that important to reset? The problem is that we have this in migration_thread(): if (current_time >= initial_time + BUFFER_DELAY) { uint64_t transferred_bytes = qemu_ftell(s->to_dst_file) - initial_bytes; uint64_t time_spent = current_time - initial_time; double bandwidth = (double)transferred_bytes / time_spent; threshold_size = bandwidth * s->parameters.downtime_limit; ... } Here qemu_ftell() would possibly be very small since we have just resumed... and then transferred_bytes will be extremely huge since "qemu_ftell(s->to_dst_file) - initial_bytes" is actually negative... Then, with luck, we'll got extremely huge "bandwidth" as well. -- Peter Xu