Re: [PATCH 07/10] Disable auto-coverge before entering COLO mode.

["Dr. David Alan Gilbert" <dgilbert@redhat.com>]

* leirao (lei.rao@intel.com) wrote:
> From: "Rao, Lei" <lei.rao@intel.com>
> 
> If we don't disable the feature of auto-converge for live migration
> before entering COLO mode, it will continue to run with COLO running,
> and eventually the system will hang due to the CPU throttle reaching
> DEFAULT_MIGRATE_MAX_CPU_THROTTLE.
> 
> Signed-off-by: Lei Rao <lei.rao@intel.com>

I don't think that's the right answer, because it would seem reasonable
to use auto-converge to ensure that a COLO snapshot succeeded by
limiting guest CPU time.  Is the right fix here to reset the state of
the auto-converge counters at the start of each colo snapshot?

Dave

> ---
>  migration/migration.c | 16 +++++++++++++++-
>  1 file changed, 15 insertions(+), 1 deletion(-)
> 
> diff --git a/migration/migration.c b/migration/migration.c
> index 31417ce..6ab37e5 100644
> --- a/migration/migration.c
> +++ b/migration/migration.c
> @@ -1673,6 +1673,20 @@ void migrate_set_block_enabled(bool value, Error **errp)
>      qapi_free_MigrationCapabilityStatusList(cap);
>  }
>  
> +static void colo_auto_converge_enabled(bool value, Error **errp)
> +{
> +    MigrationCapabilityStatusList *cap = NULL;
> +
> +    if (migrate_colo_enabled() && migrate_auto_converge()) {
> +        QAPI_LIST_PREPEND(cap,
> +                          migrate_cap_add(MIGRATION_CAPABILITY_AUTO_CONVERGE,
> +                                          value));
> +        qmp_migrate_set_capabilities(cap, errp);
> +        qapi_free_MigrationCapabilityStatusList(cap);
> +    }
> +    cpu_throttle_stop();
> +}
> +
>  static void migrate_set_block_incremental(MigrationState *s, bool value)
>  {
>      s->parameters.block_incremental = value;
> @@ -3401,7 +3415,7 @@ static MigIterateState migration_iteration_run(MigrationState *s)
>  static void migration_iteration_finish(MigrationState *s)
>  {
>      /* If we enabled cpu throttling for auto-converge, turn it off. */
> -    cpu_throttle_stop();
> +    colo_auto_converge_enabled(false, &error_abort);
>  
>      qemu_mutex_lock_iothread();
>      switch (s->state) {
> -- 
> 1.8.3.1
> 
-- 
Dr. David Alan Gilbert / dgilbert@redhat.com / Manchester, UK