Re: [PATCH v3 0/4] Allow to enable multifd and postcopy migration together

[Peter Xu <peterx@redhat.com>]

On Tue, Jan 21, 2025 at 06:40:28PM +0530, Prasad Pandit wrote:
> From: Prasad Pandit <pjp@fedoraproject.org>
> 
> Hello,
> 
> * Currently Multifd and Postcopy migration can not be used together.
>   QEMU shows "Postcopy is not yet compatible with multifd" message.
> 
>   When migrating guests with large (100's GB) RAM, Multifd threads
>   help to accelerate migration, but inability to use it with the
>   Postcopy mode delays guest start up on the destination side.
> 
> * This patch series allows to enable both Multifd and Postcopy
>   migration together. Precopy and Multifd threads work during
>   the initial guest (RAM) transfer. When migration moves to the
>   Postcopy phase, Multifd threads are restrained and the Postcopy
>   threads start to request pages from the source side.
> 
> * This series removes magic value (4-bytes) introduced in the
>   previous series for the Postcopy channel. And refactoring of
>   the 'ram_save_target_page' function is made independent of
>   the multifd & postcopy change.
> 
> * This series passes all existing 'tests/qtest/migration/*' test
>   cases and adds a new one to enable multifd channels with postcopy
>   migration.
> 
>   v2: https://lore.kernel.org/qemu-devel/20241129122256.96778-1-ppandit@redhat.com/T/#u
>   v1: https://lore.kernel.org/qemu-devel/20241126115748.118683-1-ppandit@redhat.com/T/#u
>   v0: https://lore.kernel.org/qemu-devel/20241029150908.1136894-1-ppandit@redhat.com/T/#u

Another comment for the cover letter (besides the test request): please
consider adding some changelog into cover letter whenever possible.

Normally we don't suggest a changelog only if the wholeset has been
drastically rewritten.  Otherwise having a changelog would help people
understand what has happened between the versions.

Thanks,

-- 
Peter Xu