Re: [Qemu-devel] Live migration sequence

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

* Pavel Fedin (p.fedin@samsung.com) wrote:
>  Hello!
> 
>  I would like to clarify, what is the exact live migration sequence in qemu?
> 
>  I mean - there are pre_save and post_load callbacks for VMState structures. Is there any determined
> order of calling them related to memory contents migration? In other words, is there any guarantee
> that pre_save is called before RAM migrates, and post_load is called after RAM migrates?

The pre_load/pre_save and post_load relate to the particular VMState the functions are attached to;
so if you use them on a VMState of a particular device the only thing you know is that the pre_save
is called just before the system writes the description out; and on loading the pre_load is called
just before it reads the data, and post_load just after it's read the data.

Ordering relating to RAM is a separate question; in general RAM is normally loaded before all
of the non-iterative devices.


>  The answer to this question is important for developing vITS live migration, where i have to dump
> internal ITS state into in-memory tables before the migration starts, and then get it back in cache
> on destination.

What's an ITS ?
With a related question, how big are the tables and can it change during the iterated part
of the migrate?

Dave

> 
> Kind regards,
> Pavel Fedin
> Expert Engineer
> Samsung Electronics Research center Russia
> 
> 
> 
> 
--
Dr. David Alan Gilbert / dgilbert@redhat.com / Manchester, UK