tree 8758705e99f15e9801e0c387b0b9b2b654519925
parent 083c07216ce9600ce9eb8454c9afd10f6184f093
author Muchun Song <songmuchun@bytedance.com> 1608001885 -0800
committer Greg Kroah-Hartman <gregkh@linuxfoundation.org> 1632303916 +0200

mm/page_alloc: speed up the iteration of max_order

commit 7ad69832f37e3cea8557db6df7c793905f1135e8 upstream.

When we free a page whose order is very close to MAX_ORDER and greater
than pageblock_order, it wastes some CPU cycles to increase max_order to
MAX_ORDER one by one and check the pageblock migratetype of that page
repeatedly especially when MAX_ORDER is much larger than pageblock_order.

We also should not be checking migratetype of buddy when "order ==
MAX_ORDER - 1" as the buddy pfn may be invalid, so adjust the condition.
With the new check, we don't need the max_order check anymore, so we
replace it.

Also adjust max_order initialization so that it's lower by one than
previously, which makes the code hopefully more clear.

Link: https://lkml.kernel.org/r/20201204155109.55451-1-songmuchun@bytedance.com
Fixes: d9dddbf55667 ("mm/page_alloc: prevent merging between isolated and other pageblocks")
Signed-off-by: Muchun Song <songmuchun@bytedance.com>
Acked-by: Vlastimil Babka <vbabka@suse.cz>
Reviewed-by: Oscar Salvador <osalvador@suse.de>
Reviewed-by: David Hildenbrand <david@redhat.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>