From: Johannes Weiner <hannes@xxxxxxxxxxx>
Subject: mm: fix vm-scalability regression in cgroup-aware workingset code
23047a96d7cf ("mm: workingset: per-cgroup cache thrash detection") added a
page->mem_cgroup lookup to the cache eviction, refault, and activation
paths, as well as locking to the activation path, and the vm-scalability
tests showed a regression of -23%. While the test in question is an
artificial worst-case scenario that doesn't occur in real workloads -
reading two sparse files in parallel at full CPU speed just to hammer the
LRU paths - there is still some optimizations that can be done in those
paths.
Inline the lookup functions to eliminate calls. Also, page->mem_cgroup
doesn't need to be stabilized when counting an activation; we merely need
to hold the RCU lock to prevent the memcg from being freed.
This cuts down on overhead quite a bit:
23047a96d7cfcfca 063f6715e77a7be5770d6081fe
---------------- --------------------------
%stddev %change %stddev
\ | \
21621405 +- 0% +11.3% 24069657 +- 2% vm-scalability.throughput
[linux@xxxxxxxxxxxx: drop unnecessary include file]
[hannes@xxxxxxxxxxx: add WARN_ON_ONCE()s]
Link: http://lkml.kernel.org/r/20160707194024.GA26580@xxxxxxxxxxx
Link: http://lkml.kernel.org/r/20160624175101.GA3024@xxxxxxxxxxx
Reported-by: Ye Xiaolong <xiaolong.ye@xxxxxxxxx>
Signed-off-by: Johannes Weiner <hannes@xxxxxxxxxxx>
Acked-by: Michal Hocko <mhocko@xxxxxxxx>
Cc: Vladimir Davydov <vdavydov@xxxxxxxxxxxxx>
Signed-off-by: Guenter Roeck <linux@xxxxxxxxxxxx>
Signed-off-by: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx>
---
include/linux/memcontrol.h | 43 ++++++++++++++++++++++++++++++++++-
include/linux/mm.h | 10 ++++++++
mm/memcontrol.c | 42 ----------------------------------
mm/workingset.c | 10 ++++----
4 files changed, 58 insertions(+), 47 deletions(-)
diff -puN include/linux/memcontrol.h~mm-fix-vm-scalability-regression-in-cgroup-aware-workingset-code include/linux/memcontrol.h
--- a/include/linux/memcontrol.h~mm-fix-vm-scalability-regression-in-cgroup-aware-workingset-code
+++ a/include/linux/memcontrol.h
@@ -314,7 +314,48 @@ void mem_cgroup_uncharge_list(struct lis
void mem_cgroup_migrate(struct page *oldpage, struct page *newpage);
-struct lruvec *mem_cgroup_zone_lruvec(struct zone *, struct mem_cgroup *);
+static inline struct mem_cgroup_per_zone *
+mem_cgroup_zone_zoneinfo(struct mem_cgroup *memcg, struct zone *zone)
+{
+ int nid = zone_to_nid(zone);
+ int zid = zone_idx(zone);
+
+ return &memcg->nodeinfo[nid]->zoneinfo[zid];
+}
+
+/**
+ * mem_cgroup_zone_lruvec - get the lru list vector for a zone and memcg
+ * @zone: zone of the wanted lruvec
+ * @memcg: memcg of the wanted lruvec
+ *
+ * Returns the lru list vector holding pages for the given @zone and
+ * @mem. This can be the global zone lruvec, if the memory controller
+ * is disabled.
+ */
+static inline struct lruvec *mem_cgroup_zone_lruvec(struct zone *zone,
+ struct mem_cgroup *memcg)
+{
+ struct mem_cgroup_per_zone *mz;
+ struct lruvec *lruvec;
+
+ if (mem_cgroup_disabled()) {
+ lruvec = &zone->lruvec;
+ goto out;
+ }
+
+ mz = mem_cgroup_zone_zoneinfo(memcg, zone);
+ lruvec = &mz->lruvec;
+out:
+ /*
+ * Since a node can be onlined after the mem_cgroup was created,
+ * we have to be prepared to initialize lruvec->zone here;
+ * and if offlined then reonlined, we need to reinitialize it.
+ */
+ if (unlikely(lruvec->zone != zone))
+ lruvec->zone = zone;
+ return lruvec;
+}
+
struct lruvec *mem_cgroup_page_lruvec(struct page *, struct zone *);
bool task_in_mem_cgroup(struct task_struct *task, struct mem_cgroup *memcg);
diff -puN include/linux/mm.h~mm-fix-vm-scalability-regression-in-cgroup-aware-workingset-code include/linux/mm.h
--- a/include/linux/mm.h~mm-fix-vm-scalability-regression-in-cgroup-aware-workingset-code
+++ a/include/linux/mm.h
@@ -973,11 +973,21 @@ static inline struct mem_cgroup *page_me
{
return page->mem_cgroup;
}
+static inline struct mem_cgroup *page_memcg_rcu(struct page *page)
+{
+ WARN_ON_ONCE(!rcu_read_lock_held());
+ return READ_ONCE(page->mem_cgroup);
+}
#else
static inline struct mem_cgroup *page_memcg(struct page *page)
{
return NULL;
}
+static inline struct mem_cgroup *page_memcg_rcu(struct page *page)
+{
+ WARN_ON_ONCE(!rcu_read_lock_held());
+ return NULL;
+}
#endif
/*
diff -puN mm/memcontrol.c~mm-fix-vm-scalability-regression-in-cgroup-aware-workingset-code mm/memcontrol.c
--- a/mm/memcontrol.c~mm-fix-vm-scalability-regression-in-cgroup-aware-workingset-code
+++ a/mm/memcontrol.c
@@ -323,15 +323,6 @@ EXPORT_SYMBOL(memcg_kmem_enabled_key);
#endif /* !CONFIG_SLOB */
-static struct mem_cgroup_per_zone *
-mem_cgroup_zone_zoneinfo(struct mem_cgroup *memcg, struct zone *zone)
-{
- int nid = zone_to_nid(zone);
- int zid = zone_idx(zone);
-
- return &memcg->nodeinfo[nid]->zoneinfo[zid];
-}
-
/**
* mem_cgroup_css_from_page - css of the memcg associated with a page
* @page: page of interest
@@ -944,39 +935,6 @@ static void invalidate_reclaim_iterators
iter = mem_cgroup_iter(NULL, iter, NULL))
/**
- * mem_cgroup_zone_lruvec - get the lru list vector for a zone and memcg
- * @zone: zone of the wanted lruvec
- * @memcg: memcg of the wanted lruvec
- *
- * Returns the lru list vector holding pages for the given @zone and
- * @mem. This can be the global zone lruvec, if the memory controller
- * is disabled.
- */
-struct lruvec *mem_cgroup_zone_lruvec(struct zone *zone,
- struct mem_cgroup *memcg)
-{
- struct mem_cgroup_per_zone *mz;
- struct lruvec *lruvec;
-
- if (mem_cgroup_disabled()) {
- lruvec = &zone->lruvec;
- goto out;
- }
-
- mz = mem_cgroup_zone_zoneinfo(memcg, zone);
- lruvec = &mz->lruvec;
-out:
- /*
- * Since a node can be onlined after the mem_cgroup was created,
- * we have to be prepared to initialize lruvec->zone here;
- * and if offlined then reonlined, we need to reinitialize it.
- */
- if (unlikely(lruvec->zone != zone))
- lruvec->zone = zone;
- return lruvec;
-}
-
-/**
* mem_cgroup_page_lruvec - return lruvec for isolating/putting an LRU page
* @page: the page
* @zone: zone of the page
diff -puN mm/workingset.c~mm-fix-vm-scalability-regression-in-cgroup-aware-workingset-code mm/workingset.c
--- a/mm/workingset.c~mm-fix-vm-scalability-regression-in-cgroup-aware-workingset-code
+++ a/mm/workingset.c
@@ -305,9 +305,10 @@ bool workingset_refault(void *shadow)
*/
void workingset_activation(struct page *page)
{
+ struct mem_cgroup *memcg;
struct lruvec *lruvec;
- lock_page_memcg(page);
+ rcu_read_lock();
/*
* Filter non-memcg pages here, e.g. unmap can call
* mark_page_accessed() on VDSO pages.
@@ -315,12 +316,13 @@ void workingset_activation(struct page *
* XXX: See workingset_refault() - this should return
* root_mem_cgroup even for !CONFIG_MEMCG.
*/
- if (!mem_cgroup_disabled() && !page_memcg(page))
+ memcg = page_memcg_rcu(page);
+ if (!mem_cgroup_disabled() && !memcg)
goto out;
- lruvec = mem_cgroup_zone_lruvec(page_zone(page), page_memcg(page));
+ lruvec = mem_cgroup_zone_lruvec(page_zone(page), memcg);
atomic_long_inc(&lruvec->inactive_age);
out:
- unlock_page_memcg(page);
+ rcu_read_unlock();
}
/*
_
--
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