[083/156] mm/memory_hotplug: update comment regarding zone shuffling

Commit Message

Andrew Morton Oct. 16, 2020, 2:46 a.m. UTC

From: David Hildenbrand <[e-mail]>
Subject: mm/memory_hotplug: update comment regarding zone shuffling

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.

Link: https://lkml.kernel.org/r/[e-mail]
Signed-off-by: David Hildenbrand <[e-mail]>
Reviewed-by: Wei Yang <[e-mail]>
Acked-by: Michal Hocko <[e-mail]>
Cc: Alexander Duyck <[e-mail]>
Cc: Mel Gorman <[e-mail]>
Cc: Michal Hocko <[e-mail]>
Cc: Dave Hansen <[e-mail]>
Cc: Vlastimil Babka <[e-mail]>
Cc: Wei Yang <[e-mail]>
Cc: Oscar Salvador <[e-mail]>
Cc: Mike Rapoport <[e-mail]>
Cc: Pankaj Gupta <[e-mail]>
Cc: Haiyang Zhang <[e-mail]>
Cc: "K. Y. Srinivasan" <[e-mail]>
Cc: Matthew Wilcox <[e-mail]>
Cc: Michael Ellerman <[e-mail]>
Cc: Scott Cheloha <[e-mail]>
Cc: Stephen Hemminger <[e-mail]>
Cc: Wei Liu <[e-mail]>
Signed-off-by: Andrew Morton <[e-mail]>
---

 mm/memory_hotplug.c |   11 ++++-------
 1 file changed, 4 insertions(+), 7 deletions(-)

Patch

--- a/mm/memory_hotplug.c~mm-memory_hotplug-update-comment-regarding-zone-shuffling
+++ a/mm/memory_hotplug.c
@@ -858,13 +858,10 @@  int __ref online_pages(unsigned long pfn
 	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);