mm: workingset: per-cgroup cache thrash detection
Cache thrash detection (see a528910e12ec "mm: thrash detection-based
file cache sizing" for details) currently only works on the system
level, not inside cgroups. Worse, as the refaults are compared to the
global number of active cache, cgroups might wrongfully get all their
refaults activated when their pages are hotter than those of others.
Move the refault machinery from the zone to the lruvec, and then tag
eviction entries with the memcg ID. This makes the thrash detection
work correctly inside cgroups.
[sergey.senozhatsky@gmail.com: do not return from workingset_activation() with locked rcu and page]
Signed-off-by: Johannes Weiner <hannes@cmpxchg.org>
Signed-off-by: Sergey Senozhatsky <sergey.senozhatsky@gmail.com>
Reviewed-by: Vladimir Davydov <vdavydov@virtuozzo.com>
Cc: Michal Hocko <mhocko@suse.cz>
Cc: David Rientjes <rientjes@google.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
diff --git a/mm/workingset.c b/mm/workingset.c
index 9a26a60..14bc23a 100644
--- a/mm/workingset.c
+++ b/mm/workingset.c
@@ -153,7 +153,8 @@
*/
#define EVICTION_SHIFT (RADIX_TREE_EXCEPTIONAL_ENTRY + \
- ZONES_SHIFT + NODES_SHIFT)
+ ZONES_SHIFT + NODES_SHIFT + \
+ MEM_CGROUP_ID_SHIFT)
#define EVICTION_MASK (~0UL >> EVICTION_SHIFT)
/*
@@ -166,9 +167,10 @@
*/
static unsigned int bucket_order __read_mostly;
-static void *pack_shadow(unsigned long eviction, struct zone *zone)
+static void *pack_shadow(int memcgid, struct zone *zone, unsigned long eviction)
{
eviction >>= bucket_order;
+ eviction = (eviction << MEM_CGROUP_ID_SHIFT) | memcgid;
eviction = (eviction << NODES_SHIFT) | zone_to_nid(zone);
eviction = (eviction << ZONES_SHIFT) | zone_idx(zone);
eviction = (eviction << RADIX_TREE_EXCEPTIONAL_SHIFT);
@@ -176,18 +178,21 @@
return (void *)(eviction | RADIX_TREE_EXCEPTIONAL_ENTRY);
}
-static void unpack_shadow(void *shadow, struct zone **zonep,
+static void unpack_shadow(void *shadow, int *memcgidp, struct zone **zonep,
unsigned long *evictionp)
{
unsigned long entry = (unsigned long)shadow;
- int zid, nid;
+ int memcgid, nid, zid;
entry >>= RADIX_TREE_EXCEPTIONAL_SHIFT;
zid = entry & ((1UL << ZONES_SHIFT) - 1);
entry >>= ZONES_SHIFT;
nid = entry & ((1UL << NODES_SHIFT) - 1);
entry >>= NODES_SHIFT;
+ memcgid = entry & ((1UL << MEM_CGROUP_ID_SHIFT) - 1);
+ entry >>= MEM_CGROUP_ID_SHIFT;
+ *memcgidp = memcgid;
*zonep = NODE_DATA(nid)->node_zones + zid;
*evictionp = entry << bucket_order;
}
@@ -202,11 +207,20 @@
*/
void *workingset_eviction(struct address_space *mapping, struct page *page)
{
+ struct mem_cgroup *memcg = page_memcg(page);
struct zone *zone = page_zone(page);
+ int memcgid = mem_cgroup_id(memcg);
unsigned long eviction;
+ struct lruvec *lruvec;
- eviction = atomic_long_inc_return(&zone->inactive_age);
- return pack_shadow(eviction, zone);
+ /* Page is fully exclusive and pins page->mem_cgroup */
+ VM_BUG_ON_PAGE(PageLRU(page), page);
+ VM_BUG_ON_PAGE(page_count(page), page);
+ VM_BUG_ON_PAGE(!PageLocked(page), page);
+
+ lruvec = mem_cgroup_zone_lruvec(zone, memcg);
+ eviction = atomic_long_inc_return(&lruvec->inactive_age);
+ return pack_shadow(memcgid, zone, eviction);
}
/**
@@ -221,13 +235,42 @@
bool workingset_refault(void *shadow)
{
unsigned long refault_distance;
+ unsigned long active_file;
+ struct mem_cgroup *memcg;
unsigned long eviction;
+ struct lruvec *lruvec;
unsigned long refault;
struct zone *zone;
+ int memcgid;
- unpack_shadow(shadow, &zone, &eviction);
+ unpack_shadow(shadow, &memcgid, &zone, &eviction);
- refault = atomic_long_read(&zone->inactive_age);
+ rcu_read_lock();
+ /*
+ * Look up the memcg associated with the stored ID. It might
+ * have been deleted since the page's eviction.
+ *
+ * Note that in rare events the ID could have been recycled
+ * for a new cgroup that refaults a shared page. This is
+ * impossible to tell from the available data. However, this
+ * should be a rare and limited disturbance, and activations
+ * are always speculative anyway. Ultimately, it's the aging
+ * algorithm's job to shake out the minimum access frequency
+ * for the active cache.
+ *
+ * XXX: On !CONFIG_MEMCG, this will always return NULL; it
+ * would be better if the root_mem_cgroup existed in all
+ * configurations instead.
+ */
+ memcg = mem_cgroup_from_id(memcgid);
+ if (!mem_cgroup_disabled() && !memcg) {
+ rcu_read_unlock();
+ return false;
+ }
+ lruvec = mem_cgroup_zone_lruvec(zone, memcg);
+ refault = atomic_long_read(&lruvec->inactive_age);
+ active_file = lruvec_lru_size(lruvec, LRU_ACTIVE_FILE);
+ rcu_read_unlock();
/*
* The unsigned subtraction here gives an accurate distance
@@ -249,7 +292,7 @@
inc_zone_state(zone, WORKINGSET_REFAULT);
- if (refault_distance <= zone_page_state(zone, NR_ACTIVE_FILE)) {
+ if (refault_distance <= active_file) {
inc_zone_state(zone, WORKINGSET_ACTIVATE);
return true;
}
@@ -262,7 +305,23 @@
*/
void workingset_activation(struct page *page)
{
- atomic_long_inc(&page_zone(page)->inactive_age);
+ struct mem_cgroup *memcg;
+ struct lruvec *lruvec;
+
+ memcg = lock_page_memcg(page);
+ /*
+ * Filter non-memcg pages here, e.g. unmap can call
+ * mark_page_accessed() on VDSO pages.
+ *
+ * XXX: See workingset_refault() - this should return
+ * root_mem_cgroup even for !CONFIG_MEMCG.
+ */
+ if (!mem_cgroup_disabled() && !memcg)
+ goto out;
+ lruvec = mem_cgroup_zone_lruvec(page_zone(page), memcg);
+ atomic_long_inc(&lruvec->inactive_age);
+out:
+ unlock_page_memcg(memcg);
}
/*