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Subject[PATCH v2 22/22] mm: split zone->lru_lock
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Looks like all ready for splitting zone->lru_lock into per-lruvec pieces.

lruvec locking loop protected with rcu. Memory controller already releases its
lru-vectors via rcu, lru-vectors embedded into zones never released.

Signed-off-by: Konstantin Khlebnikov <khlebnikov@openvz.org>
---
include/linux/mmzone.h | 2 -
mm/compaction.c | 2 -
mm/internal.h | 100 ++++++++++++++++++++++++++++++------------------
mm/memcontrol.c | 1
mm/page_alloc.c | 2 -
mm/swap.c | 2 -
6 files changed, 68 insertions(+), 41 deletions(-)

diff --git a/include/linux/mmzone.h b/include/linux/mmzone.h
index 9fd82b1..56995db 100644
--- a/include/linux/mmzone.h
+++ b/include/linux/mmzone.h
@@ -301,6 +301,7 @@ struct lruvec {
struct pglist_data *node;
struct zone *zone;
#endif
+ spinlock_t lru_lock;
struct list_head pages_lru[NR_LRU_LISTS];
unsigned long pages_count[NR_LRU_LISTS];

@@ -378,7 +379,6 @@ struct zone {
ZONE_PADDING(_pad1_)

/* Fields commonly accessed by the page reclaim scanner */
- spinlock_t lru_lock;
struct lruvec lruvec;

unsigned long pages_scanned; /* since last reclaim */
diff --git a/mm/compaction.c b/mm/compaction.c
index 1e89165..3fbb958 100644
--- a/mm/compaction.c
+++ b/mm/compaction.c
@@ -306,7 +306,7 @@ static isolate_migrate_t isolate_migratepages(struct zone *zone,
lruvec = NULL;
}
if (need_resched() ||
- (lruvec && spin_is_contended(&zone->lru_lock))) {
+ (lruvec && spin_is_contended(&lruvec->lru_lock))) {
if (lruvec)
unlock_lruvec_irq(lruvec);
lruvec = NULL;
diff --git a/mm/internal.h b/mm/internal.h
index a1a3206..110d653 100644
--- a/mm/internal.h
+++ b/mm/internal.h
@@ -15,76 +15,98 @@

static inline void lock_lruvec(struct lruvec *lruvec, unsigned long *flags)
{
- spin_lock_irqsave(&lruvec_zone(lruvec)->lru_lock, *flags);
+ spin_lock_irqsave(&lruvec->lru_lock, *flags);
}

static inline void lock_lruvec_irq(struct lruvec *lruvec)
{
- spin_lock_irq(&lruvec_zone(lruvec)->lru_lock);
+ spin_lock_irq(&lruvec->lru_lock);
}

static inline void unlock_lruvec(struct lruvec *lruvec, unsigned long *flags)
{
- spin_unlock_irqrestore(&lruvec_zone(lruvec)->lru_lock, *flags);
+ spin_unlock_irqrestore(&lruvec->lru_lock, *flags);
}

static inline void unlock_lruvec_irq(struct lruvec *lruvec)
{
- spin_unlock_irq(&lruvec_zone(lruvec)->lru_lock);
+ spin_unlock_irq(&lruvec->lru_lock);
}

static inline void wait_lruvec_unlock(struct lruvec *lruvec)
{
- spin_unlock_wait(&lruvec_zone(lruvec)->lru_lock);
+ spin_unlock_wait(&lruvec->lru_lock);
}

#ifdef CONFIG_CGROUP_MEM_RES_CTLR

/* Dynamic page to lruvec mapping */

+/* protected with rcu, interrupts disabled, locked_lruvec != NULL */
+static inline struct lruvec *__catch_page_lruvec(struct lruvec *locked_lruvec,
+ struct page *page)
+{
+ struct lruvec *lruvec;
+
+ do {
+ lruvec = page_lruvec(page);
+ if (likely(lruvec == locked_lruvec))
+ return lruvec;
+ spin_unlock(&locked_lruvec->lru_lock);
+ spin_lock(&lruvec->lru_lock);
+ locked_lruvec = lruvec;
+ } while (1);
+}
+
static inline struct lruvec *lock_page_lruvec(struct page *page,
unsigned long *flags)
{
- struct zone *zone = page_zone(page);
+ struct lruvec *lruvec;

- spin_lock_irqsave(&zone->lru_lock, *flags);
- return page_lruvec(page);
+ rcu_read_lock();
+ lruvec = page_lruvec(page);
+ lock_lruvec(lruvec, flags);
+ lruvec = __catch_page_lruvec(lruvec, page);
+ rcu_read_unlock();
+ return lruvec;
}

static inline struct lruvec *lock_page_lruvec_irq(struct page *page)
{
- struct zone *zone = page_zone(page);
+ struct lruvec *lruvec;

- spin_lock_irq(&zone->lru_lock);
- return page_lruvec(page);
+ rcu_read_lock();
+ lruvec = page_lruvec(page);
+ lock_lruvec_irq(lruvec);
+ lruvec = __catch_page_lruvec(lruvec, page);
+ rcu_read_unlock();
+ return lruvec;
}

static inline struct lruvec *relock_page_lruvec(struct lruvec *lruvec,
struct page *page,
unsigned long *flags)
{
- struct zone *zone = page_zone(page);
-
- if (!lruvec || zone != lruvec_zone(lruvec)) {
- if (lruvec)
- unlock_lruvec(lruvec, flags);
- lruvec = lock_page_lruvec(page, flags);
+ rcu_read_lock();
+ if (!lruvec) {
+ lruvec = page_lruvec(page);
+ lock_lruvec(lruvec, flags);
}
-
+ lruvec = __catch_page_lruvec(lruvec, page);
+ rcu_read_unlock();
return lruvec;
}

static inline struct lruvec *relock_page_lruvec_irq(struct lruvec *lruvec,
struct page *page)
{
- struct zone *zone = page_zone(page);
-
- if (!lruvec || zone != lruvec_zone(lruvec)) {
- if (lruvec)
- unlock_lruvec_irq(lruvec);
- lruvec = lock_page_lruvec_irq(page);
+ rcu_read_lock();
+ if (!lruvec) {
+ lruvec = page_lruvec(page);
+ lock_lruvec_irq(lruvec);
}
-
+ lruvec = __catch_page_lruvec(lruvec, page);
+ rcu_read_unlock();
return lruvec;
}

@@ -92,8 +114,10 @@ static inline struct lruvec *relock_page_lruvec_irq(struct lruvec *lruvec,
static inline struct lruvec *__relock_page_lruvec(struct lruvec *lruvec,
struct page *page)
{
- /* Currenyly only one lruvec per-zone */
- return page_lruvec(page);
+ rcu_read_lock();
+ lruvec = __catch_page_lruvec(lruvec, page);
+ rcu_read_unlock();
+ return lruvec;
}

/*
@@ -104,22 +128,24 @@ static inline struct lruvec *__relock_page_lruvec(struct lruvec *lruvec,
*/
static inline bool catch_page_lruvec(struct lruvec **lruvec, struct page *page)
{
- struct zone *zone;
bool ret = false;

+ rcu_read_lock();
+ /*
+ * If we see there PageLRU(), it means page has valid lruvec link.
+ * We need protect whole operation with single rcu-interval, otherwise
+ * lruvec which hold this LRU sign can run out before we secure it.
+ */
if (PageLRU(page)) {
if (!*lruvec) {
- zone = page_zone(page);
- spin_lock_irq(&zone->lru_lock);
- } else
- zone = lruvec_zone(*lruvec);
-
- if (PageLRU(page)) {
*lruvec = page_lruvec(page);
+ lock_lruvec_irq(*lruvec);
+ }
+ *lruvec = __catch_page_lruvec(*lruvec, page);
+ if (PageLRU(page))
ret = true;
- } else
- *lruvec = &zone->lruvec;
}
+ rcu_read_unlock();

return ret;
}
@@ -127,7 +153,7 @@ static inline bool catch_page_lruvec(struct lruvec **lruvec, struct page *page)
/* Wait for lruvec unlock before locking other lruvec for the same page */
static inline void __wait_lruvec_unlock(struct lruvec *lruvec)
{
- /* Currently only one lruvec per-zone */
+ wait_lruvec_unlock(lruvec);
}

#else /* CONFIG_CGROUP_MEM_RES_CTLR */
diff --git a/mm/memcontrol.c b/mm/memcontrol.c
index eb024c1..d0ca9d0 100644
--- a/mm/memcontrol.c
+++ b/mm/memcontrol.c
@@ -4648,6 +4648,7 @@ static int alloc_mem_cgroup_per_zone_info(struct mem_cgroup *memcg, int node)
INIT_LIST_HEAD(&mz->lruvec.pages_lru[lru]);
mz->lruvec.pages_count[lru] = 0;
}
+ spin_lock_init(&mz->lruvec.lru_lock);
mz->lruvec.node = NODE_DATA(node);
mz->lruvec.zone = &NODE_DATA(node)->node_zones[zone];
mz->usage_in_excess = 0;
diff --git a/mm/page_alloc.c b/mm/page_alloc.c
index 72263e4..c258024 100644
--- a/mm/page_alloc.c
+++ b/mm/page_alloc.c
@@ -4357,7 +4357,7 @@ static void __paginginit free_area_init_core(struct pglist_data *pgdat,
#endif
zone->name = zone_names[j];
spin_lock_init(&zone->lock);
- spin_lock_init(&zone->lru_lock);
+ spin_lock_init(&zone->lruvec.lru_lock);
zone_seqlock_init(zone);
zone->zone_pgdat = pgdat;

diff --git a/mm/swap.c b/mm/swap.c
index 9e81df3..43866d7 100644
--- a/mm/swap.c
+++ b/mm/swap.c
@@ -694,7 +694,7 @@ void lru_add_page_tail(struct lruvec *lruvec,
VM_BUG_ON(!PageHead(page));
VM_BUG_ON(PageCompound(page_tail));
VM_BUG_ON(PageLRU(page_tail));
- VM_BUG_ON(NR_CPUS != 1 && !spin_is_locked(&lruvec_zone(lruvec)->lru_lock));
+ VM_BUG_ON(NR_CPUS != 1 && !spin_is_locked(&lruvec->lru_lock));

SetPageLRU(page_tail);



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