Re: [PATCH v3 14/21] mm: introduce lruvec locking primitives
From: Konstantin Khlebnikov
Date: Tue Feb 28 2012 - 01:23:31 EST
KAMEZAWA Hiroyuki wrote:
On Thu, 23 Feb 2012 17:52:47 +0400
Konstantin Khlebnikov<khlebnikov@xxxxxxxxxx> wrote:
This is initial preparation for lru_lock splitting.
This locking primites designed to hide splitted nature of lru_lock
and to avoid overhead for non-splitted lru_lock in non-memcg case.
* Lock via lruvec reference
lock_lruvec(lruvec, flags)
lock_lruvec_irq(lruvec)
* Lock via page reference
lock_page_lruvec(page, flags)
lock_page_lruvec_irq(page)
relock_page_lruvec(lruvec, page, flags)
relock_page_lruvec_irq(lruvec, page)
__relock_page_lruvec(lruvec, page) ( lruvec != NULL, page in same zone )
They always returns pointer to some locked lruvec, page anyway can be
not in lru, PageLRU() sign is stable while we hold returned lruvec lock.
Caller must guarantee page to lruvec reference validity.
* Lock via page, without stable page reference
__lock_page_lruvec_irq(&lruvec, page)
It returns true of lruvec succesfully locked and PageLRU is set.
Initial lruvec can be NULL. Consequent calls must be in the same zone.
* Unlock
unlock_lruvec(lruvec, flags)
unlock_lruvec_irq(lruvec)
* Wait
wait_lruvec_unlock(lruvec)
Wait for lruvec unlock, caller must have stable reference to lruvec.
__wait_lruvec_unlock(lruvec)
Wait for lruvec unlock before locking other lrulock for same page,
nothing if there only one possible lruvec per page.
Used at page-to-lruvec reference switching to stabilize PageLRU sign.
Signed-off-by: Konstantin Khlebnikov<khlebnikov@xxxxxxxxxx>
O.K. I like this.
Acked-by: KAMEZAWA Hiroyuki<kamezawa.hiroyu@xxxxxxxxxxxxxx>
Hmm....Could you add a comment in memcg part ? (see below)
---
mm/huge_memory.c | 8 +-
mm/internal.h | 176 ++++++++++++++++++++++++++++++++++++++++++++++++++++++
mm/memcontrol.c | 14 ++--
mm/swap.c | 58 ++++++------------
mm/vmscan.c | 77 ++++++++++--------------
5 files changed, 237 insertions(+), 96 deletions(-)
diff --git a/mm/huge_memory.c b/mm/huge_memory.c
index 09e7069..74996b8 100644
--- a/mm/huge_memory.c
+++ b/mm/huge_memory.c
@@ -1228,13 +1228,11 @@ static int __split_huge_page_splitting(struct page *page,
static void __split_huge_page_refcount(struct page *page)
{
int i;
- struct zone *zone = page_zone(page);
struct lruvec *lruvec;
int tail_count = 0;
/* prevent PageLRU to go away from under us, and freeze lru stats */
- spin_lock_irq(&zone->lru_lock);
- lruvec = page_lruvec(page);
+ lruvec = lock_page_lruvec_irq(page);
compound_lock(page);
/* complete memcg works before add pages to LRU */
mem_cgroup_split_huge_fixup(page);
@@ -1316,11 +1314,11 @@ static void __split_huge_page_refcount(struct page *page)
BUG_ON(atomic_read(&page->_count)<= 0);
__dec_zone_page_state(page, NR_ANON_TRANSPARENT_HUGEPAGES);
- __mod_zone_page_state(zone, NR_ANON_PAGES, HPAGE_PMD_NR);
+ __mod_zone_page_state(lruvec_zone(lruvec), NR_ANON_PAGES, HPAGE_PMD_NR);
ClearPageCompound(page);
compound_unlock(page);
- spin_unlock_irq(&zone->lru_lock);
+ unlock_lruvec_irq(lruvec);
for (i = 1; i< HPAGE_PMD_NR; i++) {
struct page *page_tail = page + i;
diff --git a/mm/internal.h b/mm/internal.h
index ef49dbf..9454752 100644
--- a/mm/internal.h
+++ b/mm/internal.h
@@ -13,6 +13,182 @@
#include<linux/mm.h>
+static inline void lock_lruvec(struct lruvec *lruvec, unsigned long *flags)
+{
+ spin_lock_irqsave(&lruvec_zone(lruvec)->lru_lock, *flags);
+}
+
+static inline void lock_lruvec_irq(struct lruvec *lruvec)
+{
+ spin_lock_irq(&lruvec_zone(lruvec)->lru_lock);
+}
+
+static inline void unlock_lruvec(struct lruvec *lruvec, unsigned long *flags)
+{
+ spin_unlock_irqrestore(&lruvec_zone(lruvec)->lru_lock, *flags);
+}
+
+static inline void unlock_lruvec_irq(struct lruvec *lruvec)
+{
+ spin_unlock_irq(&lruvec_zone(lruvec)->lru_lock);
+}
+
+static inline void wait_lruvec_unlock(struct lruvec *lruvec)
+{
+ spin_unlock_wait(&lruvec_zone(lruvec)->lru_lock);
+}
+
+#ifdef CONFIG_CGROUP_MEM_RES_CTLR
+
+/* Dynamic page to lruvec mapping */
+
+/* Lock other lruvec for other page in the same zone */
+static inline struct lruvec *__relock_page_lruvec(struct lruvec *locked_lruvec,
+ struct page *page)
+{
+ /* Currenyly only one lru_lock per-zone */
+ return page_lruvec(page);
+}
+
+static inline struct lruvec *relock_page_lruvec_irq(struct lruvec *lruvec,
+ struct page *page)
+{
+ struct zone *zone = page_zone(page);
+
+ if (!lruvec) {
+ spin_lock_irq(&zone->lru_lock);
+ } else if (zone != lruvec_zone(lruvec)) {
+ unlock_lruvec_irq(lruvec);
+ spin_lock_irq(&zone->lru_lock);
+ }
+ return page_lruvec(page);
+}
Could you add comments/caution to the caller
- !PageLRU(page) case ?
- Can the caller assume page_lruvec(page) == lruvec ? If no, which lru_vec is locked ?
Yes, caller can assume page_lruvec(page) == lruvec. And PageLRU() is stable,
it means it stays true or false while this lruvec is locked.
etc...
+
+static inline struct lruvec *relock_page_lruvec(struct lruvec *lruvec,
+ struct page *page,
+ unsigned long *flags)
+{
+ struct zone *zone = page_zone(page);
+
+ if (!lruvec) {
+ spin_lock_irqsave(&zone->lru_lock, *flags);
+ } else if (zone != lruvec_zone(lruvec)) {
+ unlock_lruvec(lruvec, flags);
+ spin_lock_irqsave(&zone->lru_lock, *flags);
+ }
+ return page_lruvec(page);
+}
Same here.
Thanks,
-Kame
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