Re: [PATCH v7 2/2] mm/memory hotplug/unplug: Optimize zone->contiguous update when changes pfn range

[Li, Tianyou]

On 1/7/2026 4:25 AM, David Hildenbrand (Red Hat) wrote:
> One more thing, the fact that the clear_zone_contiguous() happens in 
> move_pfn_range_to_zone() is a bit suboptimal.
>
> Maybe we need a comment here like
>
> /*
>  * Calculate the new zone contig state before move_pfn_range_to_zone()
>  * sets the zone temporarily to non-contiguous.
>  */
>
> Or something like that.
Will change accordingly. Thanks.


> Alternatively, we have to rework the code a bit that this dependency 
> is a bit clearer.


Agreed, probably we can have this optimization first then explore a more 
explicit approach for the zone contiguous state management.


> > +    new_contiguous_state = zone_contig_state_after_growing(zone, 
> > pfn, nr_pages);
> >         /* associate pfn range with the zone */
> >       move_pfn_range_to_zone(zone, pfn, nr_pages, NULL, MIGRATE_MOVABLE,
> > @@ -1204,7 +1273,7 @@ int online_pages(unsigned long pfn, unsigned 
> > long nr_pages,
> >       }
> >         online_pages_range(pfn, nr_pages);
> > -    set_zone_contiguous(zone);
> > +    set_zone_contiguous(zone, new_contiguous_state);
> >       adjust_present_page_count(pfn_to_page(pfn), group, nr_pages);

Regards,

Tianyou