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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: Rik van Riel <riel@redhat.com>
Cc: Andrea Arcangeli <aarcange@redhat.com>
Acked-by: Mel 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: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
This commit is contained in:
Rik van Riel 2012-03-21 16:33:52 -07:00 committed by Linus Torvalds
parent 7be62de99a
commit aff622495c
5 changed files with 27 additions and 8 deletions
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14
include/linux/compaction.h
View File

@ -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;
}

1
include/linux/mmzone.h
View File

@ -365,6 +365,7 @@ struct zone {
*/
unsigned int compact_considered;
unsigned int compact_defer_shift;
int compact_order_failed;
#endif
ZONE_PADDING(_pad1_)

12
mm/compaction.c
View File

@ -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));
}

6
mm/page_alloc.c
View File

@ -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();
}

2
mm/vmscan.c
View File

@ -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 */