From 42a300353577ccc17ecc627b8570a89fa1678bec Mon Sep 17 00:00:00 2001 From: Johannes Weiner Date: Tue, 14 May 2019 15:47:12 -0700 Subject: mm: memcontrol: fix recursive statistics correctness & scalabilty Right now, when somebody needs to know the recursive memory statistics and events of a cgroup subtree, they need to walk the entire subtree and sum up the counters manually. There are two issues with this: 1. When a cgroup gets deleted, its stats are lost. The state counters should all be 0 at that point, of course, but the events are not. When this happens, the event counters, which are supposed to be monotonic, can go backwards in the parent cgroups. 2. During regular operation, we always have a certain number of lazily freed cgroups sitting around that have been deleted, have no tasks, but have a few cache pages remaining. These groups' statistics do not change until we eventually hit memory pressure, but somebody watching, say, memory.stat on an ancestor has to iterate those every time. This patch addresses both issues by introducing recursive counters at each level that are propagated from the write side when stats change. Upward propagation happens when the per-cpu caches spill over into the local atomic counter. This is the same thing we do during charge and uncharge, except that the latter uses atomic RMWs, which are more expensive; stat changes happen at around the same rate. In a sparse file test (page faults and reclaim at maximum CPU speed) with 5 cgroup nesting levels, perf shows __mod_memcg_page state at ~1%. Link: http://lkml.kernel.org/r/20190412151507.2769-4-hannes@cmpxchg.org Signed-off-by: Johannes Weiner Reviewed-by: Shakeel Butt Reviewed-by: Roman Gushchin Cc: Michal Hocko Signed-off-by: Andrew Morton Signed-off-by: Linus Torvalds --- include/linux/memcontrol.h | 54 +++++++++++++++++++++++++++++++++++++++++++--- 1 file changed, 51 insertions(+), 3 deletions(-) (limited to 'include/linux') diff --git a/include/linux/memcontrol.h b/include/linux/memcontrol.h index e35e6a651187..bc74d6a4407c 100644 --- a/include/linux/memcontrol.h +++ b/include/linux/memcontrol.h @@ -128,6 +128,7 @@ struct mem_cgroup_per_node { struct lruvec_stat __percpu *lruvec_stat_cpu; atomic_long_t lruvec_stat[NR_VM_NODE_STAT_ITEMS]; + atomic_long_t lruvec_stat_local[NR_VM_NODE_STAT_ITEMS]; unsigned long lru_zone_size[MAX_NR_ZONES][NR_LRU_LISTS]; @@ -279,8 +280,12 @@ struct mem_cgroup { MEMCG_PADDING(_pad2_); atomic_long_t vmstats[MEMCG_NR_STAT]; + atomic_long_t vmstats_local[MEMCG_NR_STAT]; + atomic_long_t vmevents[NR_VM_EVENT_ITEMS]; - atomic_long_t memory_events[MEMCG_NR_MEMORY_EVENTS]; + atomic_long_t vmevents_local[NR_VM_EVENT_ITEMS]; + + atomic_long_t memory_events[MEMCG_NR_MEMORY_EVENTS]; unsigned long socket_pressure; @@ -550,6 +555,20 @@ struct mem_cgroup *lock_page_memcg(struct page *page); void __unlock_page_memcg(struct mem_cgroup *memcg); void unlock_page_memcg(struct page *page); +/* + * idx can be of type enum memcg_stat_item or node_stat_item. + * Keep in sync with memcg_exact_page_state(). + */ +static inline unsigned long memcg_page_state(struct mem_cgroup *memcg, int idx) +{ + long x = atomic_long_read(&memcg->vmstats[idx]); +#ifdef CONFIG_SMP + if (x < 0) + x = 0; +#endif + return x; +} + /* * idx can be of type enum memcg_stat_item or node_stat_item. * Keep in sync with memcg_exact_page_state(). @@ -557,7 +576,7 @@ void unlock_page_memcg(struct page *page); static inline unsigned long memcg_page_state_local(struct mem_cgroup *memcg, int idx) { - long x = atomic_long_read(&memcg->vmstats[idx]); + long x = atomic_long_read(&memcg->vmstats_local[idx]); #ifdef CONFIG_SMP if (x < 0) x = 0; @@ -609,6 +628,24 @@ static inline void mod_memcg_page_state(struct page *page, mod_memcg_state(page->mem_cgroup, idx, val); } +static inline unsigned long lruvec_page_state(struct lruvec *lruvec, + enum node_stat_item idx) +{ + struct mem_cgroup_per_node *pn; + long x; + + if (mem_cgroup_disabled()) + return node_page_state(lruvec_pgdat(lruvec), idx); + + pn = container_of(lruvec, struct mem_cgroup_per_node, lruvec); + x = atomic_long_read(&pn->lruvec_stat[idx]); +#ifdef CONFIG_SMP + if (x < 0) + x = 0; +#endif + return x; +} + static inline unsigned long lruvec_page_state_local(struct lruvec *lruvec, enum node_stat_item idx) { @@ -619,7 +656,7 @@ static inline unsigned long lruvec_page_state_local(struct lruvec *lruvec, return node_page_state(lruvec_pgdat(lruvec), idx); pn = container_of(lruvec, struct mem_cgroup_per_node, lruvec); - x = atomic_long_read(&pn->lruvec_stat[idx]); + x = atomic_long_read(&pn->lruvec_stat_local[idx]); #ifdef CONFIG_SMP if (x < 0) x = 0; @@ -959,6 +996,11 @@ static inline void mem_cgroup_print_oom_group(struct mem_cgroup *memcg) { } +static inline unsigned long memcg_page_state(struct mem_cgroup *memcg, int idx) +{ + return 0; +} + static inline unsigned long memcg_page_state_local(struct mem_cgroup *memcg, int idx) { @@ -989,6 +1031,12 @@ static inline void mod_memcg_page_state(struct page *page, { } +static inline unsigned long lruvec_page_state(struct lruvec *lruvec, + enum node_stat_item idx) +{ + return node_page_state(lruvec_pgdat(lruvec), idx); +} + static inline unsigned long lruvec_page_state_local(struct lruvec *lruvec, enum node_stat_item idx) { -- cgit v1.2.3