Re: [Qemu-devel] VM-Migration

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

* 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