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

[Peter Xu]

On Mon, Jul 22, 2024 at 05:07:57PM -0300, Fabiano Rosas wrote:
> 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.

Fair point.

> 
> > 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.

Maybe it's simply that the helper itself (multifd_send_zero_page_detect)
needs a better name (perhaps multifd_send_ram_setup()?). I'm ok we leave
this one as-is:

Reviewed-by: Peter Xu <peterx@redhat.com>

-- 
Peter Xu