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-rw-r--r--mm/compaction.c65
1 files changed, 45 insertions, 20 deletions
diff --git a/mm/compaction.c b/mm/compaction.c
index b16dd3822995..832c4183dccc 100644
--- a/mm/compaction.c
+++ b/mm/compaction.c
@@ -50,6 +50,11 @@ static inline bool migrate_async_suitable(int migratetype)
return is_migrate_cma(migratetype) || migratetype == MIGRATE_MOVABLE;
}
+static inline bool should_release_lock(spinlock_t *lock)
+{
+ return need_resched() || spin_is_contended(lock);
+}
+
/*
* Compaction requires the taking of some coarse locks that are potentially
* very heavily contended. Check if the process needs to be scheduled or
@@ -62,7 +67,7 @@ static inline bool migrate_async_suitable(int migratetype)
static bool compact_checklock_irqsave(spinlock_t *lock, unsigned long *flags,
bool locked, struct compact_control *cc)
{
- if (need_resched() || spin_is_contended(lock)) {
+ if (should_release_lock(lock)) {
if (locked) {
spin_unlock_irqrestore(lock, *flags);
locked = false;
@@ -327,7 +332,7 @@ isolate_migratepages_range(struct zone *zone, struct compact_control *cc,
isolate_mode_t mode = 0;
struct lruvec *lruvec;
unsigned long flags;
- bool locked;
+ bool locked = false;
/*
* Ensure that there are not too many pages isolated from the LRU
@@ -347,23 +352,17 @@ isolate_migratepages_range(struct zone *zone, struct compact_control *cc,
/* Time to isolate some pages for migration */
cond_resched();
- spin_lock_irqsave(&zone->lru_lock, flags);
- locked = true;
for (; low_pfn < end_pfn; low_pfn++) {
struct page *page;
/* give a chance to irqs before checking need_resched() */
- if (!((low_pfn+1) % SWAP_CLUSTER_MAX)) {
- spin_unlock_irqrestore(&zone->lru_lock, flags);
- locked = false;
+ if (locked && !((low_pfn+1) % SWAP_CLUSTER_MAX)) {
+ if (should_release_lock(&zone->lru_lock)) {
+ spin_unlock_irqrestore(&zone->lru_lock, flags);
+ locked = false;
+ }
}
- /* Check if it is ok to still hold the lock */
- locked = compact_checklock_irqsave(&zone->lru_lock, &flags,
- locked, cc);
- if (!locked || fatal_signal_pending(current))
- break;
-
/*
* migrate_pfn does not necessarily start aligned to a
* pageblock. Ensure that pfn_valid is called when moving
@@ -403,21 +402,40 @@ isolate_migratepages_range(struct zone *zone, struct compact_control *cc,
pageblock_nr = low_pfn >> pageblock_order;
if (!cc->sync && last_pageblock_nr != pageblock_nr &&
!migrate_async_suitable(get_pageblock_migratetype(page))) {
- low_pfn += pageblock_nr_pages;
- low_pfn = ALIGN(low_pfn, pageblock_nr_pages) - 1;
- last_pageblock_nr = pageblock_nr;
- continue;
+ goto next_pageblock;
}
+ /* Check may be lockless but that's ok as we recheck later */
if (!PageLRU(page))
continue;
/*
- * PageLRU is set, and lru_lock excludes isolation,
- * splitting and collapsing (collapsing has already
- * happened if PageLRU is set).
+ * PageLRU is set. lru_lock normally excludes isolation
+ * splitting and collapsing (collapsing has already happened
+ * if PageLRU is set) but the lock is not necessarily taken
+ * here and it is wasteful to take it just to check transhuge.
+ * Check TransHuge without lock and skip the whole pageblock if
+ * it's either a transhuge or hugetlbfs page, as calling
+ * compound_order() without preventing THP from splitting the
+ * page underneath us may return surprising results.
*/
if (PageTransHuge(page)) {
+ if (!locked)
+ goto next_pageblock;
+ low_pfn += (1 << compound_order(page)) - 1;
+ continue;
+ }
+
+ /* Check if it is ok to still hold the lock */
+ locked = compact_checklock_irqsave(&zone->lru_lock, &flags,
+ locked, cc);
+ if (!locked || fatal_signal_pending(current))
+ break;
+
+ /* Recheck PageLRU and PageTransHuge under lock */
+ if (!PageLRU(page))
+ continue;
+ if (PageTransHuge(page)) {
low_pfn += (1 << compound_order(page)) - 1;
continue;
}
@@ -444,6 +462,13 @@ isolate_migratepages_range(struct zone *zone, struct compact_control *cc,
++low_pfn;
break;
}
+
+ continue;
+
+next_pageblock:
+ low_pfn += pageblock_nr_pages;
+ low_pfn = ALIGN(low_pfn, pageblock_nr_pages) - 1;
+ last_pageblock_nr = pageblock_nr;
}
acct_isolated(zone, locked, cc);