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

[David Hildenbrand (Red Hat)]

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.

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

> +	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);

--
Cheers

David