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

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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>
This commit is contained in:
Mel Gorman 2009-06-16 15:31:58 -07:00 committed by Linus Torvalds
parent 11e33f6a55
commit 49255c619f
2 changed files with 4 additions and 3 deletions
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3
include/linux/mmzone.h
View File

@ -50,9 +50,6 @@ extern int page_group_by_mobility_disabled;
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);
}

4
mm/page_alloc.c
View File

@ -168,6 +168,10 @@ int page_group_by_mobility_disabled __read_mostly;
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,
PB_migrate, PB_migrate_end);
}