[Qemu-devel] VM-Migration

[Qemu-devel] VM-Migration

[Pradeep Kiruvale]

Hi All,

Is it possible to enable/disable to migration features on the fly for a
qemu VM?
I mean through qmp interface kind of a interface?

I am asking this because keeping the dirty memory list, this could consume
some
compute and memory. So, the plan is to enable when the VM needs to be
migrated.

Please clarify.

Regards,
Pradeep

Re: [Qemu-devel] VM-Migration

[Dr. David Alan Gilbert]

* Pradeep Kiruvale (pradeepkiruvale@gmail.com) wrote:
> Hi All,
> 
> Is it possible to enable/disable to migration features on the fly for a
> qemu VM?
> I mean through qmp interface kind of a interface?
> 
> I am asking this because keeping the dirty memory list, this could consume
> some
> compute and memory. So, the plan is to enable when the VM needs to be
> migrated.
> 
> Please clarify.

These bitmaps should already only be allocated during the migration process,
so you shouldn't be seeing any overhead during normal running.

See migration/ram.c ram_save_setup->ram_state_init which allocates
ram_bitmap and that only happens at the start of migration.
ram_state_init also calls memory_global_dirty_log_start which does
the kernel side of it.

Dave

> Regards,
> Pradeep
--
Dr. David Alan Gilbert / dgilbert@redhat.com / Manchester, UK

Re: [Qemu-devel] VM-Migration

[Pradeep Kiruvale]

On 26 April 2017 at 18:14, Dr. David Alan Gilbert <dgilbert@redhat.com>
wrote:

> * Pradeep Kiruvale (pradeepkiruvale@gmail.com) wrote:
> > Hi All,
> >
> > Is it possible to enable/disable to migration features on the fly for a
> > qemu VM?
> > I mean through qmp interface kind of a interface?
> >
> > I am asking this because keeping the dirty memory list, this could
> consume
> > some
> > compute and memory. So, the plan is to enable when the VM needs to be
> > migrated.
> >
> > Please clarify.
>
> These bitmaps should already only be allocated during the migration
> process,
> so you shouldn't be seeing any overhead during normal running.
>
> See migration/ram.c ram_save_setup->ram_state_init which allocates
> ram_bitmap and that only happens at the start of migration.
> ram_state_init also calls memory_global_dirty_log_start which does
> the kernel side of it.
>
>
Thanks for the clarification Dave!.

-Pradeep

Dave
>
> > Regards,
> > Pradeep
> --
> Dr. David Alan Gilbert / dgilbert@redhat.com / Manchester, UK
>