[PATCH RFC 10/15] mm: handle book relocks in compaction

Konstantin Khlebnikov
2012-02-15T22:57:47Z

Prepare for lru_lock splitting in memory compaction code.

Signed-off-by: Konstantin Khlebnikov <khlebnikov@openvz.org>
---
mm/compaction.c | 32 ++++++++++++++++++++------------
1 files changed, 20 insertions(+), 12 deletions(-)

diff --git a/mm/compaction.c b/mm/compaction.c
index 680a725..f521edf 100644
--- a/mm/compaction.c
+++ b/mm/compaction.c
@@ -269,7 +269,7 @@ static isolate_migrate_t isolate_migratepages(struct zone *zone,
unsigned long nr_scanned = 0, nr_isolated = 0;
struct list_head *migratelist = &cc->migratepages;
isolate_mode_t mode = ISOLATE_ACTIVE|ISOLATE_INACTIVE;
- struct book *book;
+ struct book *book = NULL;

/* Do not scan outside zone boundaries */
low_pfn = max(cc->migrate_pfn, zone->zone_start_pfn);
@@ -301,25 +301,23 @@ static isolate_migrate_t isolate_migratepages(struct zone *zone,

/* Time to isolate some pages for migration */
cond_resched();
- spin_lock_irq(&zone->lru_lock);
for (; low_pfn < end_pfn; low_pfn++) {
struct page *page;
- bool locked = true;

/* give a chance to irqs before checking need_resched() */
if (!((low_pfn+1) % SWAP_CLUSTER_MAX)) {
- spin_unlock_irq(&zone->lru_lock);
- locked = false;
+ if (book)
+ unlock_book_irq(book);
+ book = NULL;
}
if (need_resched() || spin_is_contended(&zone->lru_lock)) {
- if (locked)
- spin_unlock_irq(&zone->lru_lock);
+ if (book)
+ unlock_book_irq(book);
+ book = NULL;
cond_resched();
- spin_lock_irq(&zone->lru_lock);
if (fatal_signal_pending(current))
break;
- } else if (!locked)
- spin_lock_irq(&zone->lru_lock);
+ }

/*
* migrate_pfn does not necessarily start aligned to a
@@ -345,6 +343,7 @@ static isolate_migrate_t isolate_migratepages(struct zone *zone,
* as memory compaction should not move pages between nodes.
*/
page = pfn_to_page(low_pfn);
+
if (page_zone(page) != zone)
continue;

@@ -369,6 +368,14 @@ static isolate_migrate_t isolate_migratepages(struct zone *zone,
if (!PageLRU(page))
continue;

+ if (book)
+ book = __relock_page_book(book, page);
+ else
+ book = lock_page_book_irq(page);
+
+ if (!PageLRU(page))
+ continue;
+
/*
* PageLRU is set, and lru_lock excludes isolation,
* splitting and collapsing (collapsing has already
@@ -389,7 +396,6 @@ static isolate_migrate_t isolate_migratepages(struct zone *zone,
VM_BUG_ON(PageTransCompound(page));

/* Successfully isolated */
- book = page_book(page);
del_page_from_lru_list(book, page, page_lru(page));
list_add(&page->lru, migratelist);
cc->nr_migratepages++;
@@ -402,9 +408,11 @@ static isolate_migrate_t isolate_migratepages(struct zone *zone,
}
}

+ if (book)
+ unlock_book_irq(book);
+
acct_isolated(zone, cc);

- spin_unlock_irq(&zone->lru_lock);
cc->migrate_pfn = low_pfn;

trace_mm_compaction_isolate_migratepages(nr_scanned, nr_isolated);