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Re: [Qemu-devel] Live migration sequence
From: |
Dr. David Alan Gilbert |
Subject: |
Re: [Qemu-devel] Live migration sequence |
Date: |
Fri, 9 Oct 2015 16:29:42 +0100 |
User-agent: |
Mutt/1.5.24 (2015-08-30) |
* Pavel Fedin (address@hidden) 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 / address@hidden / Manchester, UK