Re: [PATCH v1 5/5] mm/memory_hotplug: update comment regarding zone shuffling

Michal Hocko
2020-10-02T13:42:00Z

On Mon 28-09-20 20:21:10, David Hildenbrand wrote:
> As we no longer shuffle via generic_online_page() and when undoing
> isolation, we can simplify the comment.
>
> We now effectively shuffle only once (properly) when onlining new
> memory.
>
> Cc: Andrew Morton <akpm@linux-foundation.org>
> Cc: Alexander Duyck <alexander.h.duyck@linux.intel.com>
> Cc: Mel Gorman <mgorman@techsingularity.net>
> Cc: Michal Hocko <mhocko@kernel.org>
> Cc: Dave Hansen <dave.hansen@intel.com>
> Cc: Vlastimil Babka <vbabka@suse.cz>
> Cc: Wei Yang <richard.weiyang@linux.alibaba.com>
> Cc: Oscar Salvador <osalvador@suse.de>
> Cc: Mike Rapoport <rppt@kernel.org>
> Signed-off-by: David Hildenbrand <david@redhat.com>

Acked-by: Michal Hocko <mhocko@suse.com>

> ---
> mm/memory_hotplug.c | 11 ++++-------
> 1 file changed, 4 insertions(+), 7 deletions(-)
>
> diff --git a/mm/memory_hotplug.c b/mm/memory_hotplug.c
> index 9db80ee29caa..c589bd8801bb 100644
> --- a/mm/memory_hotplug.c
> +++ b/mm/memory_hotplug.c
> @@ -859,13 +859,10 @@ int __ref online_pages(unsigned long pfn, unsigned long nr_pages,
> undo_isolate_page_range(pfn, pfn + nr_pages, MIGRATE_MOVABLE);
>
> /*
> - * When exposing larger, physically contiguous memory areas to the
> - * buddy, shuffling in the buddy (when freeing onlined pages, putting
> - * them either to the head or the tail of the freelist) is only helpful
> - * for maintaining the shuffle, but not for creating the initial
> - * shuffle. Shuffle the whole zone to make sure the just onlined pages
> - * are properly distributed across the whole freelist. Make sure to
> - * shuffle once pageblocks are no longer isolated.
> + * Freshly onlined pages aren't shuffled (e.g., all pages are placed to
> + * the tail of the freelist when undoing isolation). Shuffle the whole
> + * zone to make sure the just onlined pages are properly distributed
> + * across the whole freelist - to create an initial shuffle.
> */
> shuffle_zone(zone);
>
> --
> 2.26.2

--
Michal Hocko
SUSE Labs