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Commit b92a6edd authored by Mel Gorman's avatar Mel Gorman Committed by Linus Torvalds
Browse files

Add a configure option to group pages by mobility 



The grouping mechanism has some memory overhead and a more complex allocation
path.  This patch allows the strategy to be disabled for small memory systems
or if it is known the workload is suffering because of the strategy.  It also
acts to show where the page groupings strategy interacts with the standard
buddy allocator.

Signed-off-by: default avatarMel Gorman <mel@csn.ul.ie>
Signed-off-by: default avatarJoel Schopp <jschopp@austin.ibm.com>
Cc: Andy Whitcroft <apw@shadowen.org>
Signed-off-by: default avatarAndrew Morton <akpm@linux-foundation.org>
Signed-off-by: default avatarLinus Torvalds <torvalds@linux-foundation.org>
parent 535131e6

include/linux/mmzone.h

+6 −0
Original line number Diff line number Diff line
@@ -33,9 +33,15 @@ 
 */

#define PAGE_ALLOC_COSTLY_ORDER 3



#ifdef CONFIG_PAGE_GROUP_BY_MOBILITY

#define MIGRATE_UNMOVABLE     0

#define MIGRATE_MOVABLE       1

#define MIGRATE_TYPES         2

#else

#define MIGRATE_UNMOVABLE     0

#define MIGRATE_MOVABLE       0

#define MIGRATE_TYPES         1

#endif



#define for_each_migratetype_order(order, type) \

	for (order = 0; order < MAX_ORDER; order++) \

init/Kconfig

+13 −0
Original line number Diff line number Diff line
@@ -607,6 +607,19 @@ config BASE_SMALL 
	default 0 if BASE_FULL

	default 1 if !BASE_FULL



config PAGE_GROUP_BY_MOBILITY

	bool "Group pages based on their mobility in the page allocator"

	def_bool y

	help

	  The standard allocator will fragment memory over time which means

	  that high order allocations will fail even if kswapd is running. If

	  this option is set, the allocator will try and group page types

	  based on their ability to migrate or reclaim. This is a best effort

	  attempt at lowering fragmentation which a few workloads care about.

	  The loss is a more complex allocator that may perform slower. If

	  you are interested in working with large pages, say Y and set

	  /proc/sys/vm/min_free_bytes to 16374. Otherwise say N



menuconfig MODULES

	bool "Enable loadable module support"

	help

mm/page_alloc.c

+37 −14
Original line number Diff line number Diff line
@@ -158,6 +158,7 @@ int nr_node_ids __read_mostly = MAX_NUMNODES; 
EXPORT_SYMBOL(nr_node_ids);

#endif



#ifdef CONFIG_PAGE_GROUP_BY_MOBILITY

static inline int get_pageblock_migratetype(struct page *page)

{

	return get_pageblock_flags_group(page, PB_migrate, PB_migrate_end);
@@ -174,6 +175,22 @@ static inline int gfpflags_to_migratetype(gfp_t gfp_flags) 
	return ((gfp_flags & __GFP_MOVABLE) != 0);

}



#else

static inline int get_pageblock_migratetype(struct page *page)

{

	return MIGRATE_UNMOVABLE;

}



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

{

}



static inline int gfpflags_to_migratetype(gfp_t gfp_flags)

{

	return MIGRATE_UNMOVABLE;

}

#endif /* CONFIG_PAGE_GROUP_BY_MOBILITY */



#ifdef CONFIG_DEBUG_VM

static int page_outside_zone_boundaries(struct zone *zone, struct page *page)

{
@@ -653,6 +670,7 @@ static int prep_new_page(struct page *page, int order, gfp_t gfp_flags) 
	return 0;

}



#ifdef CONFIG_PAGE_GROUP_BY_MOBILITY

/*

 * This array describes the order lists are fallen back to when

 * the free lists for the desirable migrate type are depleted
@@ -709,6 +727,13 @@ static struct page *__rmqueue_fallback(struct zone *zone, int order, 


	return NULL;

}

#else

static struct page *__rmqueue_fallback(struct zone *zone, int order,

						int start_migratetype)

{

	return NULL;

}

#endif /* CONFIG_PAGE_GROUP_BY_MOBILITY */



/* 

 * Do the hard work of removing an element from the buddy allocator.
@@ -953,27 +978,25 @@ again: 
			if (unlikely(!pcp->count))

				goto failed;

		}



#ifdef CONFIG_PAGE_GROUP_BY_MOBILITY

		/* Find a page of the appropriate migrate type */

		list_for_each_entry(page, &pcp->list, lru) {

			if (page_private(page) == migratetype) {

				list_del(&page->lru);

				pcp->count--;

		list_for_each_entry(page, &pcp->list, lru)

			if (page_private(page) == migratetype)

				break;

			}

		}



		/*

		 * Check if a page of the appropriate migrate type

		 * was found. If not, allocate more to the pcp list

		 */

		if (&page->lru == &pcp->list) {

		/* Allocate more to the pcp list if necessary */

		if (unlikely(&page->lru == &pcp->list)) {

			pcp->count += rmqueue_bulk(zone, 0,

					pcp->batch, &pcp->list, migratetype);

			page = list_entry(pcp->list.next, struct page, lru);

			VM_BUG_ON(page_private(page) != migratetype);

		}

#else

		page = list_entry(pcp->list.next, struct page, lru);

#endif /* CONFIG_PAGE_GROUP_BY_MOBILITY */



		list_del(&page->lru);

		pcp->count--;

		}

	} else {

		spin_lock_irqsave(&zone->lock, flags);

		page = __rmqueue(zone, order, migratetype);