Re: [Qemu-devel] [PATCH v3 3/5] migration: Dynamic cpu throttling for auto-converge

[Jason J. Herne]

On 06/26/2015 01:54 PM, Dr. David Alan Gilbert wrote:
> * Jason J. Herne (address@hidden) wrote:
...
> > diff --git a/migration/migration.c b/migration/migration.c
> > index 05790e9..7708c54 100644
> > --- a/migration/migration.c
> > +++ b/migration/migration.c
> > @@ -25,6 +25,7 @@
> >   #include "qemu/thread.h"
> >   #include "qmp-commands.h"
> >   #include "trace.h"
> > +#include "qom/cpu.h"
> >
> >   #define MAX_THROTTLE  (32 << 20)      /* Migration speed throttling */
> >
> > @@ -858,6 +859,9 @@ static void *migration_thread(void *opaque)
> >           }
> >       }
> >
> > +    /* If we enabled cpu throttling for auto-converge, turn it off. */
> > +    cpu_throttle_stop();
> > +
> >       qemu_mutex_lock_iothread();
> >       if (s->state == MIGRATION_STATUS_COMPLETED) {
> >           int64_t end_time = qemu_clock_get_ms(QEMU_CLOCK_REALTIME);
>
> Is that cpu_throttle_stop() sufficient if I use 'migration cancel'
> so that next time through it's all reset so that there's no throttling
> at the beginning?

It will be reset when cpu_throttle_set is called again when auto-converge
re-enables throttling for the next migration. This happens in patch 3,
mig_throttle_guest_down():

Basically, cpu_throttle_set requires the user to provide a throttling
percentage. So starting a new throttling operation will overwrite the
previous value.

--
-- Jason J. Herne (address@hidden)