Re: [Qemu-devel] [PATCH COLO-Frame (Base) v21 03/17] migration: Enter into COLO mode after migration if COLO is enabled

[Amit Shah]

On (Wed) 26 Oct 2016 [21:49:10], Hailiang Zhang wrote:
> On 2016/10/26 12:50, Amit Shah wrote:
> >On (Tue) 18 Oct 2016 [20:09:59], zhanghailiang wrote:
> >>Add a new migration state: MIGRATION_STATUS_COLO. Migration source side
> >>enters this state after the first live migration successfully finished
> >>if COLO is enabled by command 'migrate_set_capability x-colo on'.
> >>
> >>We reuse migration thread, so the process of checkpointing will be handled
> >>in migration thread.
> >>
> >>Signed-off-by: zhanghailiang <address@hidden>
> >>Signed-off-by: Li Zhijian <address@hidden>
> >>Signed-off-by: Gonglei <address@hidden>
> >>Reviewed-by: Dr. David Alan Gilbert <address@hidden>
> >
> >(snip)
> >
> >>+static void colo_process_checkpoint(MigrationState *s)
> >>+{
> >>+    qemu_mutex_lock_iothread();
> >>+    vm_start();
> >>+    qemu_mutex_unlock_iothread();
> >>+    trace_colo_vm_state_change("stop", "run");
> >>+
> >>+    /* TODO: COLO checkpoint savevm loop */
> >>+
> >>+    migrate_set_state(&s->state, MIGRATION_STATUS_COLO,
> >>+                      MIGRATION_STATUS_COMPLETED);
> >
> >Is this just a temporary thing that'll be removed in the next patches?
> 
> Yes, you are right, we will move this codes into failover process in the next
> patch, because after failover, we should finish the original migration, there
> are still some cleanup work need to be done.
> 
> >I guess so - because once you enter COLO state, you want to remain in
> >it, right?
> >
> 
> Yes.
> 
> >I think the commit message implies that.  So the commit msg and the
> >code are not in sync.
> >
> 
> Hmm, i'll remove it here in this patch, is it OK ?

Yes.

> 
> >(snip)
> >
> >>diff --git a/migration/migration.c b/migration/migration.c
> >>index f7dd9c6..462007d 100644
> >>--- a/migration/migration.c
> >>+++ b/migration/migration.c
> >>@@ -695,6 +695,10 @@ MigrationInfo *qmp_query_migrate(Error **errp)
> >>
> >>          get_xbzrle_cache_stats(info);
> >>          break;
> >>+    case MIGRATION_STATUS_COLO:
> >>+        info->has_status = true;
> >>+        /* TODO: display COLO specific information (checkpoint info etc.) 
> >>*/
> >>+        break;
> >
> >When do you plan to add this?  I guess it's important for debugging
> >and also to get the state of the system while colo is active.  What
> >info do you have planned to display here?
> >
> 
> IIRC, we have such patch which implemented this specific information in the 
> previous
> version long time ago. Yes, it is quit useful, for example, the average/max 
> time of
> pause while do checkpoint, the average/max number of dirty pages transferred 
> to SVM,
> the amount time of VM in COLO state, the total checkpoint times, the count of
> checkpointing because of inconsistency of network packages compare.

Yes, please get this in soon as well.


                Amit