Re: Live Migration ToDo

[Peter Xu]

On Tue, Apr 26, 2022 at 02:17:41AM +0300, Artyom wrote:
> Yes, the original postcopy paper (
> https://kartikgopalan.github.io/publications/hines09postcopy_osr.pdf)
> suggests optimizations. For example, prepaging uses hints from the VM's
> page access patterns to reduce both the number of major network faults and
> the duration of the migration phase. After examining the code in
> migration/, I could not find any mention of these optimizations. Perhaps
> the ideas from the paper have already been tried to implement in QEMU, but
> they were abandoned?

They're partly implemented, afaict.

See ram_find_and_save_block(), if we got a postcopy requested page we'll by
default remember it in rs->last_page and we'll do forward-direction-only
bubbling since we'll start to send follow up pages from there.

We also have free page reportings too with virtio-balloon device's
existance.

I don't think we have double-direction bubbling, or multi-pivot bubbling.
I'm not sure whether they were discussed/abandoned or not.  I think Dave
should know the best so I'll leave the rest to him..

-- 
Peter Xu