Re: [PATCH 08/10] mm/page_alloc: use get_onbuddy_migratetype() to get buddy list type

From: Vlastimil Babka
Date: Tue Jul 08 2014 - 03:23:21 EST

On 07/08/2014 03:01 AM, Gioh Kim wrote:

2014-07-08 ìì 12:57, Vlastimil Babka ì ê:
On 07/04/2014 09:57 AM, Joonsoo Kim wrote:
When isolating free page, what we want to know is which list
the page is linked. If it is linked in isolate migratetype buddy list,
we can skip watermark check and freepage counting. And if it is linked
in CMA migratetype buddy list, we need to fixup freepage counting. For
this purpose, get_onbuddy_migratetype() is more fit and cheap than
get_pageblock_migratetype(). So use it.

Hm but you made get_onbuddy_migratetype() work only with CONFIG_MEMORY_ISOLATION. And __isolate_free_page is (despite the name) not at all limited to CONFIG_MEMORY_ISOLATION.

Current __isolate_free_page is called by only split_free_page, and split_free_page by isolate_freepages_block.
split_free_page is called only for isolated pages now but It can be changed someday.

Yeah, but isolate_freepages_block is also not part of CONFIG_MEMORY_ISOLATION. Unfortunately, there are two distinct concepts of memory isolation and LRU isolation, that are not distinguished in function names.

I think get_onbuddy_migratetype should work with any situation.

And I think the name of get_onbuddy_migratetype is confused.
Because of _onbuddy_, it might look like that the pages are buddy pages.
I think the original name _freepage_ is proper one.

Signed-off-by: Joonsoo Kim <>
mm/page_alloc.c | 2 +-
1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/mm/page_alloc.c b/mm/page_alloc.c
index e1c4c3e..d9fb8bb 100644
--- a/mm/page_alloc.c
+++ b/mm/page_alloc.c
@@ -1597,7 +1597,7 @@ static int __isolate_free_page(struct page *page, unsigned int order)

zone = page_zone(page);
- mt = get_pageblock_migratetype(page);
+ mt = get_onbuddy_migratetype(page);

if (!is_migrate_isolate(mt)) {
/* Obey watermarks as if the page was being allocated */

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