Re: [RFC PATCH v2 6/9] migration/multifd: Move pages accounting into multifd_send_zero_page_detect()

[Fabiano Rosas <farosas@suse.de>]

Peter Xu <peterx@redhat.com> writes:

> On Mon, Jul 22, 2024 at 02:59:11PM -0300, Fabiano Rosas wrote:
>> All references to pages are being removed from the multifd worker
>> threads in order to allow multifd to deal with different payload
>> types.
>> 
>> multifd_send_zero_page_detect() is called by all multifd migration
>> paths that deal with pages and is the last spot where zero pages and
>> normal page amounts are adjusted. Move the pages accounting into that
>> function.
>
> True, but it's a bit hackish to update (especially, normal) page counters
> in a zero page detect function.

Hm, that's the one place in the code that actually sets
normal_num. Seems adequate to me.

> I understand you want to move pages out of the thread function, that's
> fair. How about put it in your new multifd_ram_fill_packet()?
>

That one is skipped when mapped-ram is in use. I could move it to
nocomp_send_prepare() after the zero_page_detect. It seems we're moving
towards changing nocomp -> ram at some point anyway. Would that be
better? It would duplicate the call due to the compression code.