This patch started off as a cleanup: __split_huge_page_refcounts() has to
cope with two scenarios, when the hugepage being split is already on LRU,
and when it is not; but why does it have to split that accounting across
three different sites? Consolidate it in lru_add_page_tail(), handling
evictable and unevictable alike, and use standard add_page_to_lru_list()
when accounting is needed (when the head is not yet on LRU).
But a recent regression in -next, I guess the removal of PageCgroupAcctLRU
test from mem_cgroup_split_huge_fixup(), makes this now a necessary fix:
under load, the MEM_CGROUP_ZSTAT count was wrapping to a huge number,
messing up reclaim calculations and causing a freeze at rmdir of cgroup.
Add a VM_BUG_ON to mem_cgroup_lru_del_list() when we're about to wrap
that count - this has not been the only such incident. Document that
lru_add_page_tail() is for Transparent HugePages by #ifdef around it.
Signed-off-by: Hugh Dickins <hughd@xxxxxxxxxx>
---
I think this is a fix to
memcg: simplify LRU handling by new rule
but I've not tried applying immediately after that one,
just on top of next minus Mel's 11/11.
mm/huge_memory.c | 10 ----------
mm/memcontrol.c | 12 ++----------
mm/swap.c | 29 +++++++++++++++++++----------
3 files changed, 21 insertions(+), 30 deletions(-)
--- mmotm.orig/mm/huge_memory.c 2011-12-22 02:53:31.884041564 -0800
+++ mmotm/mm/huge_memory.c 2011-12-28 12:53:23.416367861 -0800
@@ -1229,7 +1229,6 @@ static void __split_huge_page_refcount(s
{
int i;
struct zone *zone = page_zone(page);
- int zonestat;
int tail_count = 0;
/* prevent PageLRU to go away from under us, and freeze lru stats */
@@ -1317,15 +1316,6 @@ static void __split_huge_page_refcount(s
__dec_zone_page_state(page, NR_ANON_TRANSPARENT_HUGEPAGES);
__mod_zone_page_state(zone, NR_ANON_PAGES, HPAGE_PMD_NR);
- /*
- * A hugepage counts for HPAGE_PMD_NR pages on the LRU statistics,
- * so adjust those appropriately if this page is on the LRU.
- */
- if (PageLRU(page)) {
- zonestat = NR_LRU_BASE + page_lru(page);
- __mod_zone_page_state(zone, zonestat, -(HPAGE_PMD_NR-1));
- }
-
ClearPageCompound(page);
compound_unlock(page);
spin_unlock_irq(&zone->lru_lock);
--- mmotm.orig/mm/memcontrol.c 2011-12-22 02:53:31.892041564 -0800
+++ mmotm/mm/memcontrol.c 2011-12-28 12:53:23.420367847 -0800
@@ -1076,6 +1076,7 @@ void mem_cgroup_lru_del_list(struct page
VM_BUG_ON(!memcg);
mz = page_cgroup_zoneinfo(memcg, page);
/* huge page split is done under lru_lock. so, we have no races. */
+ VM_BUG_ON(MEM_CGROUP_ZSTAT(mz, lru) < (1 << compound_order(page)));
MEM_CGROUP_ZSTAT(mz, lru) -= 1 << compound_order(page);
}
@@ -2468,9 +2469,7 @@ static void __mem_cgroup_commit_charge(s
void mem_cgroup_split_huge_fixup(struct page *head)
{
struct page_cgroup *head_pc = lookup_page_cgroup(head);
- struct mem_cgroup_per_zone *mz;
struct page_cgroup *pc;
- enum lru_list lru;
int i;
if (mem_cgroup_disabled())
@@ -2481,15 +2480,8 @@ void mem_cgroup_split_huge_fixup(struct
smp_wmb();/* see __commit_charge() */
pc->flags = head_pc->flags & ~PCGF_NOCOPY_AT_SPLIT;
}
- /*
- * Tail pages will be added to LRU.
- * We hold lru_lock,then,reduce counter directly.
- */
- lru = page_lru(head);
- mz = page_cgroup_zoneinfo(head_pc->mem_cgroup, head);
- MEM_CGROUP_ZSTAT(mz, lru) -= HPAGE_PMD_NR - 1;
}
-#endif
+#endif /* CONFIG_TRANSPARENT_HUGEPAGE */
/**
* mem_cgroup_move_account - move account of the page
--- mmotm.orig/mm/swap.c 2011-12-28 12:32:02.764338005 -0800
+++ mmotm/mm/swap.c 2011-12-28 12:53:23.420367847 -0800
@@ -650,6 +650,7 @@ void __pagevec_release(struct pagevec *p
EXPORT_SYMBOL(__pagevec_release);
+#ifdef CONFIG_TRANSPARENT_HUGEPAGE
/* used by __split_huge_page_refcount() */
void lru_add_page_tail(struct zone* zone,
struct page *page, struct page *page_tail)
@@ -666,8 +667,6 @@ void lru_add_page_tail(struct zone* zone
SetPageLRU(page_tail);
if (page_evictable(page_tail, NULL)) {
- struct lruvec *lruvec;
-
if (PageActive(page)) {
SetPageActive(page_tail);
active = 1;
@@ -677,18 +676,28 @@ void lru_add_page_tail(struct zone* zone
lru = LRU_INACTIVE_ANON;
}
update_page_reclaim_stat(zone, page_tail, file, active);
- lruvec = mem_cgroup_lru_add_list(zone, page_tail, lru);
- if (likely(PageLRU(page)))
- list_add(&page_tail->lru, page->lru.prev);
- else
- list_add(&page_tail->lru, lruvec->lists[lru].prev);
- __mod_zone_page_state(zone, NR_LRU_BASE + lru,
- hpage_nr_pages(page_tail));
} else {
SetPageUnevictable(page_tail);
- add_page_to_lru_list(zone, page_tail, LRU_UNEVICTABLE);
+ lru = LRU_UNEVICTABLE;
+ }
+
+ if (likely(PageLRU(page)))
+ list_add_tail(&page_tail->lru, &page->lru);
+ else {
+ struct list_head *list_head;
+ /*
+ * Head page has not yet been counted, as an hpage,
+ * so we must account for each subpage individually.
+ *
+ * Use the standard add function to put page_tail on the list,
+ * but then correct its position so they all end up in order.
+ */
+ add_page_to_lru_list(zone, page_tail, lru);
+ list_head = page_tail->lru.prev;
+ list_move_tail(&page_tail->lru, list_head);
}
}
+#endif /* CONFIG_TRANSPARENT_HUGEPAGE */
static void ____pagevec_lru_add_fn(struct page *page, void *arg)
{
--
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