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Commit aff62249 authored by Rik van Riel's avatar Rik van Riel Committed by Linus Torvalds
Browse files

vmscan: only defer compaction for failed order and higher 



Currently a failed order-9 (transparent hugepage) compaction can lead to
memory compaction being temporarily disabled for a memory zone.  Even if
we only need compaction for an order 2 allocation, eg.  for jumbo frames
networking.

The fix is relatively straightforward: keep track of the highest order at
which compaction is succeeding, and only defer compaction for orders at
which compaction is failing.

Signed-off-by: default avatarRik van Riel <riel@redhat.com>
Cc: Andrea Arcangeli <aarcange@redhat.com>
Acked-by: default avatarMel Gorman <mel@csn.ul.ie>
Cc: Johannes Weiner <hannes@cmpxchg.org>
Cc: Minchan Kim <minchan.kim@gmail.com>
Cc: KOSAKI Motohiro <kosaki.motohiro@jp.fujitsu.com>
Cc: Hillf Danton <dhillf@gmail.com>
Signed-off-by: default avatarAndrew Morton <akpm@linux-foundation.org>
Signed-off-by: default avatarLinus Torvalds <torvalds@linux-foundation.org>
parent 7be62de9

include/linux/compaction.h

+10 −4
Original line number Diff line number Diff line
@@ -34,20 +34,26 @@ extern unsigned long compaction_suitable(struct zone *zone, int order); 
 * allocation success. 1 << compact_defer_limit compactions are skipped up

 * to a limit of 1 << COMPACT_MAX_DEFER_SHIFT

 */

static inline void defer_compaction(struct zone *zone)

static inline void defer_compaction(struct zone *zone, int order)

{

	zone->compact_considered = 0;

	zone->compact_defer_shift++;



	if (order < zone->compact_order_failed)

		zone->compact_order_failed = order;



	if (zone->compact_defer_shift > COMPACT_MAX_DEFER_SHIFT)

		zone->compact_defer_shift = COMPACT_MAX_DEFER_SHIFT;

}



/* Returns true if compaction should be skipped this time */

static inline bool compaction_deferred(struct zone *zone)

static inline bool compaction_deferred(struct zone *zone, int order)

{

	unsigned long defer_limit = 1UL << zone->compact_defer_shift;



	if (order < zone->compact_order_failed)

		return false;



	/* Avoid possible overflow */

	if (++zone->compact_considered > defer_limit)

		zone->compact_considered = defer_limit;
@@ -73,11 +79,11 @@ static inline unsigned long compaction_suitable(struct zone *zone, int order) 
	return COMPACT_SKIPPED;

}



static inline void defer_compaction(struct zone *zone)

static inline void defer_compaction(struct zone *zone, int order)

{

}



static inline bool compaction_deferred(struct zone *zone)

static inline bool compaction_deferred(struct zone *zone, int order)

{

	return 1;

}

include/linux/mmzone.h

+1 −0
Original line number Diff line number Diff line
@@ -365,6 +365,7 @@ struct zone { 
	 */

	unsigned int		compact_considered;

	unsigned int		compact_defer_shift;

	int			compact_order_failed;

#endif



	ZONE_PADDING(_pad1_)

mm/compaction.c

+11 −1
Original line number Diff line number Diff line
@@ -695,9 +695,19 @@ static int __compact_pgdat(pg_data_t *pgdat, struct compact_control *cc) 
		INIT_LIST_HEAD(&cc->freepages);

		INIT_LIST_HEAD(&cc->migratepages);



		if (cc->order < 0 || !compaction_deferred(zone))

		if (cc->order < 0 || !compaction_deferred(zone, cc->order))

			compact_zone(zone, cc);



		if (cc->order > 0) {

			int ok = zone_watermark_ok(zone, cc->order,

						low_wmark_pages(zone), 0, 0);

			if (ok && cc->order > zone->compact_order_failed)

				zone->compact_order_failed = cc->order + 1;

			/* Currently async compaction is never deferred. */

			else if (!ok && cc->sync)

				defer_compaction(zone, cc->order);

		}



		VM_BUG_ON(!list_empty(&cc->freepages));

		VM_BUG_ON(!list_empty(&cc->migratepages));

	}

mm/page_alloc.c

+4 −2
Original line number Diff line number Diff line
@@ -1990,7 +1990,7 @@ __alloc_pages_direct_compact(gfp_t gfp_mask, unsigned int order, 
	if (!order)

		return NULL;



	if (compaction_deferred(preferred_zone)) {

	if (compaction_deferred(preferred_zone, order)) {

		*deferred_compaction = true;

		return NULL;

	}
@@ -2012,6 +2012,8 @@ __alloc_pages_direct_compact(gfp_t gfp_mask, unsigned int order, 
		if (page) {

			preferred_zone->compact_considered = 0;

			preferred_zone->compact_defer_shift = 0;

			if (order >= preferred_zone->compact_order_failed)

				preferred_zone->compact_order_failed = order + 1;

			count_vm_event(COMPACTSUCCESS);

			return page;

		}
@@ -2028,7 +2030,7 @@ __alloc_pages_direct_compact(gfp_t gfp_mask, unsigned int order, 
		 * defer if the failure was a sync compaction failure.

		 */

		if (sync_migration)

			defer_compaction(preferred_zone);

			defer_compaction(preferred_zone, order);



		cond_resched();

	}

mm/vmscan.c

+1 −1
Original line number Diff line number Diff line
@@ -2198,7 +2198,7 @@ static inline bool compaction_ready(struct zone *zone, struct scan_control *sc) 
	 * If compaction is deferred, reclaim up to a point where

	 * compaction will have a chance of success when re-enabled

	 */

	if (compaction_deferred(zone))

	if (compaction_deferred(zone, sc->order))

		return watermark_ok;



	/* If compaction is not ready to start, keep reclaiming */