mm: compaction: abort compaction loop if lock is contended or run too long

isolate_migratepages_range() might isolate no pages if for example when
zone->lru_lock is contended and running asynchronous compaction. In this
case, we should abort compaction, otherwise, compact_zone will run a
useless loop and make zone->lru_lock is even contended.

An additional check is added to ensure that cc.migratepages and
cc.freepages get properly drained whan compaction is aborted.

[minchan@kernel.org: Putback pages isolated for migration if aborting]
[akpm@linux-foundation.org: compact_zone_order requires non-NULL arg contended]
[akpm@linux-foundation.org: make compact_zone_order() require non-NULL arg `contended']
[minchan@kernel.org: Putback pages isolated for migration if aborting]
Signed-off-by: Andrea Arcangeli <aarcange@redhat.com>
Signed-off-by: Shaohua Li <shli@fusionio.com>
Signed-off-by: Mel Gorman <mgorman@suse.de>
Acked-by: Minchan Kim <minchan@kernel.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

diff --git a/mm/compaction.c b/mm/compaction.c
index 1f61bcbd62627f2df0097f83f0d23135b7c4139a..0649cc1b3479daf56bc1a3b995b7c5c5ef59dd9d 100644 (file)
--- a/mm/compaction.c
+++ b/mm/compaction.c
@@ -70,8 +70,7 @@ static bool compact_checklock_irqsave(spinlock_t *lock, unsigned long *flags,
 
                /* async aborts if taking too long or contended */
                if (!cc->sync) {
-                       if (cc->contended)
-                               *cc->contended = true;
+                       cc->contended = true;
                        return false;
                }
 
@@ -688,7 +687,7 @@ static isolate_migrate_t isolate_migratepages(struct zone *zone,
 
        /* Perform the isolation */
        low_pfn = isolate_migratepages_range(zone, cc, low_pfn, end_pfn);
-       if (!low_pfn)
+       if (!low_pfn || cc->contended)
                return ISOLATE_ABORT;
 
        cc->migrate_pfn = low_pfn;
@@ -848,6 +847,8 @@ static int compact_zone(struct zone *zone, struct compact_control *cc)
                switch (isolate_migratepages(zone, cc)) {
                case ISOLATE_ABORT:
                        ret = COMPACT_PARTIAL;
+                       putback_lru_pages(&cc->migratepages);
+                       cc->nr_migratepages = 0;
                        goto out;
                case ISOLATE_NONE:
                        continue;
@@ -896,6 +897,7 @@ static unsigned long compact_zone_order(struct zone *zone,
                                 bool sync, bool *contended,
                                 struct page **page)
 {
+       unsigned long ret;
        struct compact_control cc = {
                .nr_freepages = 0,
                .nr_migratepages = 0,
@@ -903,13 +905,18 @@ static unsigned long compact_zone_order(struct zone *zone,
                .migratetype = allocflags_to_migratetype(gfp_mask),
                .zone = zone,
                .sync = sync,
-               .contended = contended,
                .page = page,
        };
        INIT_LIST_HEAD(&cc.freepages);
        INIT_LIST_HEAD(&cc.migratepages);
 
-       return compact_zone(zone, &cc);
+       ret = compact_zone(zone, &cc);
+
+       VM_BUG_ON(!list_empty(&cc.freepages));
+       VM_BUG_ON(!list_empty(&cc.migratepages));
+
+       *contended = cc.contended;
+       return ret;
 }
 
 int sysctl_extfrag_threshold = 500;

diff --git a/mm/internal.h b/mm/internal.h
index 96cda4c6ac56762f69a919f7fe9332666be98930..97664be2ca378107b7729a78dc58e09eff54b99d 100644 (file)
--- a/mm/internal.h
+++ b/mm/internal.h
@@ -130,7 +130,7 @@ struct compact_control {
        int order;                      /* order a direct compactor needs */
        int migratetype;                /* MOVABLE, RECLAIMABLE etc */
        struct zone *zone;
-       bool *contended;                /* True if a lock was contended */
+       bool contended;                 /* True if a lock was contended */
        struct page **page;             /* Page captured of requested size */
 };