Commit 204dfefe authored by Wei Yang's avatar Wei Yang Committed by Andrew Morton
Browse files

mm/page_alloc: find_large_buddy() from start_pfn aligned order 

We iterate pfn from order 0 to MAX_PAGE_ORDER aligned to find large buddy.
While if the order is less than start_pfn aligned order, we would get the
same pfn and do the same check again.

Iterate from start_pfn aligned order to reduce duplicated work.

[richard.weiyang@gmail.com: add comment on assignment of order]
  Link: https://lkml.kernel.org/r/20250828091618.7869-1-richard.weiyang@gmail.com
  Link: https://lkml.kernel.org/r/20250902025807.11467-1-richard.weiyang@gmail.com
Link: https://lkml.kernel.org/r/20250828091618.7869-1-richard.weiyang@gmail.com
Link: https://lkml.kernel.org/r/20250902025807.11467-1-richard.weiyang@gmail.com


Signed-off-by: default avatarWei Yang <richard.weiyang@gmail.com>
Reviewed-by: default avatarZi Yan <ziy@nvidia.com>
Acked-by: default avatarJohannes Weiner <hannes@cmpxchg.org>
Reviewed-by: default avatarVishal Moola (Oracle) <vishal.moola@gmail.com>
Reviewed-by: default avatarVlastimil Babka <vbabka@suse.cz>
Cc: David Hildenbrand <david@redhat.com>
Signed-off-by: default avatarAndrew Morton <akpm@linux-foundation.org>
parent c66ae644

mm/page_alloc.c

+7 −1
Original line number Diff line number Diff line
@@ -2033,7 +2033,13 @@ static int move_freepages_block(struct zone *zone, struct page *page, 
/* Look for a buddy that straddles start_pfn */

static unsigned long find_large_buddy(unsigned long start_pfn)

{

	int order = 0;

	/*

	 * If start_pfn is not an order-0 PageBuddy, next PageBuddy containing

	 * start_pfn has minimal order of __ffs(start_pfn) + 1. Start checking

	 * the order with __ffs(start_pfn). If start_pfn is order-0 PageBuddy,

	 * the starting order does not matter.

	 */

	int order = start_pfn ? __ffs(start_pfn) : MAX_PAGE_ORDER;

	struct page *page;

	unsigned long pfn = start_pfn;