From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from eggs.gnu.org ([2001:4830:134:3::10]:56839) by lists.gnu.org with esmtp (Exim 4.71) (envelope-from ) id 1ZEgYZ-0005Cx-Ot for qemu-devel@nongnu.org; Mon, 13 Jul 2015 12:26:16 -0400 Received: from Debian-exim by eggs.gnu.org with spam-scanned (Exim 4.71) (envelope-from ) id 1ZEgYV-0002IX-Fl for qemu-devel@nongnu.org; Mon, 13 Jul 2015 12:26:15 -0400 Received: from mx1.redhat.com ([209.132.183.28]:55445) by eggs.gnu.org with esmtp (Exim 4.71) (envelope-from ) id 1ZEgYV-0002ID-8P for qemu-devel@nongnu.org; Mon, 13 Jul 2015 12:26:11 -0400 From: Juan Quintela In-Reply-To: <20150713155310.GH2492@work-vm> (David Alan Gilbert's message of "Mon, 13 Jul 2015 16:53:10 +0100") References: <1434450415-11339-1-git-send-email-dgilbert@redhat.com> <1434450415-11339-24-git-send-email-dgilbert@redhat.com> <87y4ikjo1n.fsf@neno.neno> <20150713155310.GH2492@work-vm> Date: Mon, 13 Jul 2015 18:26:07 +0200 Message-ID: <87vbdohvmo.fsf@neno.neno> MIME-Version: 1.0 Content-Type: text/plain Subject: Re: [Qemu-devel] [PATCH v7 23/42] MIGRATION_STATUS_POSTCOPY_ACTIVE: Add new migration state Reply-To: quintela@redhat.com List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , To: "Dr. David Alan Gilbert" 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 "Dr. David Alan Gilbert" wrote: > * Juan Quintela (quintela@redhat.com) wrote: >> "Dr. David Alan Gilbert (git)" wrote: >> > From: "Dr. David Alan Gilbert" >> > >> > 'MIGRATION_STATUS_POSTCOPY_ACTIVE' is entered after migrate_start_postcopy >> > >> > 'migration_postcopy_phase' is provided for other sections to know if >> > they're in postcopy. >> > >> > Signed-off-by: Dr. David Alan Gilbert >> > Reviewed-by: David Gibson >> > Reviewed-by: Eric Blake >> >> Reviewed-by: Juan Quintela >> >> >> But (there is always a but....) >> >> >> > @@ -358,6 +359,39 @@ MigrationInfo *qmp_query_migrate(Error **errp) >> > >> > get_xbzrle_cache_stats(info); >> > break; >> > + case MIGRATION_STATUS_POSTCOPY_ACTIVE: >> > + /* Mostly the same as active; TODO add some postcopy stats */ >> > + info->has_status = true; >> > + info->has_total_time = true; >> > + info->total_time = qemu_clock_get_ms(QEMU_CLOCK_REALTIME) >> > + - s->total_time; >> > + info->has_expected_downtime = true; >> > + info->expected_downtime = s->expected_downtime; >> > + info->has_setup_time = true; >> > + info->setup_time = s->setup_time; >> > + >> > + info->has_ram = true; >> > + info->ram = g_malloc0(sizeof(*info->ram)); >> > + info->ram->transferred = ram_bytes_transferred(); >> > + info->ram->remaining = ram_bytes_remaining(); >> > + info->ram->total = ram_bytes_total(); >> > + info->ram->duplicate = dup_mig_pages_transferred(); >> > + info->ram->skipped = skipped_mig_pages_transferred(); >> > + info->ram->normal = norm_mig_pages_transferred(); >> > + info->ram->normal_bytes = norm_mig_bytes_transferred(); >> > + info->ram->dirty_pages_rate = s->dirty_pages_rate; >> > + info->ram->mbps = s->mbps; >> > + >> > + if (blk_mig_active()) { >> > + info->has_disk = true; >> > + info->disk = g_malloc0(sizeof(*info->disk)); >> > + info->disk->transferred = blk_mig_bytes_transferred(); >> > + info->disk->remaining = blk_mig_bytes_remaining(); >> > + info->disk->total = blk_mig_bytes_total(); >> > + } >> >> Can we have block migration active with postcopy? I would assume that >> this would get disk corruption, no? Or if you preffer the other >> question, what protects us from disk corruption? > > I think you can, I've not tried it; however I also think it should > be safe. > > migration/block.c's block_save_pending always puts a value in the > non_postcopiable_pending return value (and 0 in the postcopiable_pending); > the migrate thread checks the non_postcopiable_pending size to > decide when it can switch to postcopy, and performs a call to the complete > method on each device before it does. Thus the block migration should > be finished before we start doing the actual postcopy stage, and thus > before the destination CPU starts running. I mean that as it is right now, the info under blk_mig_active() check would be zero/the same than before entering postcopy. > > A possibly harder question is what happens if block.c did implement > postcopy and you had both block postcopy and ram postcopy active at > the same time; again I think it should work but I'm not sure if one > would starve the other. > >> Once here, I guess we can get the migrate_already_active() bit without >> problem? > > I'm not sure of the question here; but the idea of migration_already_active() > is just to avoid all of the open-coded checks for each possible state; > now we've added anothe state they were getting messy. Sorry. I mean that the migrate_already_active() bits can get in without further ado. Don't need to wait for postcopy to be integrated. > > Dave > >> >> Later, Juan. > -- > Dr. David Alan Gilbert / dgilbert@redhat.com / Manchester, UK