Commit 49255c61 authored Jun 16, 2009 by Mel Gorman Committed by Linus Torvalds Jun 16, 2009

page allocator: move check for disabled anti-fragmentation out of fastpath



On low-memory systems, anti-fragmentation gets disabled as there is
nothing it can do and it would just incur overhead shuffling pages between
lists constantly.  Currently the check is made in the free page fast path
for every page.  This patch moves it to a slow path.  On machines with low
memory, there will be small amount of additional overhead as pages get
shuffled between lists but it should quickly settle.

Signed-off-by: Mel Gorman <mel@csn.ul.ie>
Reviewed-by: Christoph Lameter <cl@linux-foundation.org>
Reviewed-by: KOSAKI Motohiro <kosaki.motohiro@jp.fujitsu.com>
Cc: Pekka Enberg <penberg@cs.helsinki.fi>
Cc: Peter Zijlstra <a.p.zijlstra@chello.nl>
Cc: Nick Piggin <nickpiggin@yahoo.com.au>
Cc: Dave Hansen <dave@linux.vnet.ibm.com>
Cc: Lee Schermerhorn <Lee.Schermerhorn@hp.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

parent 11e33f6a

include/linux/mmzone.h

+0 −3

Original line number	Original line	Diff line number	Diff line
	@@ -50,9 +50,6 @@ extern int page_group_by_mobility_disabled;

	static inline int get_pageblock_migratetype(struct page *page)		static inline int get_pageblock_migratetype(struct page *page)
	{		{
	if (unlikely(page_group_by_mobility_disabled))
	return MIGRATE_UNMOVABLE;

	return get_pageblock_flags_group(page, PB_migrate, PB_migrate_end);		return get_pageblock_flags_group(page, PB_migrate, PB_migrate_end);
	}		}

mm/page_alloc.c

+4 −0

Original line number	Original line	Diff line number	Diff line
	@@ -168,6 +168,10 @@ int page_group_by_mobility_disabled __read_mostly;

	static void set_pageblock_migratetype(struct page *page, int migratetype)		static void set_pageblock_migratetype(struct page *page, int migratetype)
	{		{

			if (unlikely(page_group_by_mobility_disabled))
			migratetype = MIGRATE_UNMOVABLE;

	set_pageblock_flags_group(page, (unsigned long)migratetype,		set_pageblock_flags_group(page, (unsigned long)migratetype,
	PB_migrate, PB_migrate_end);		PB_migrate, PB_migrate_end);
	}		}

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