From 55779ec759ccc3c12b917b3712a7716e1140c652 Mon Sep 17 00:00:00 2001 From: Johannes Weiner Date: Thu, 28 Jul 2016 15:45:10 -0700 Subject: mm: fix vm-scalability regression in cgroup-aware workingset code Commit 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@roeck-us.net: drop unnecessary include file] [hannes@cmpxchg.org: add WARN_ON_ONCE()s] Link: http://lkml.kernel.org/r/20160707194024.GA26580@cmpxchg.org Link: http://lkml.kernel.org/r/20160624175101.GA3024@cmpxchg.org Reported-by: Ye Xiaolong Signed-off-by: Johannes Weiner Acked-by: Michal Hocko Cc: Vladimir Davydov Signed-off-by: Guenter Roeck Signed-off-by: Andrew Morton Signed-off-by: Linus Torvalds --- 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 --git a/include/linux/memcontrol.h b/include/linux/memcontrol.h index 71aff733a497..1c4df4420258 100644 --- a/include/linux/memcontrol.h +++ b/include/linux/memcontrol.h @@ -314,7 +314,48 @@ void mem_cgroup_uncharge_list(struct list_head *page_list); 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 --git a/include/linux/mm.h b/include/linux/mm.h index c606fe4f9a7f..97065e1f0237 100644 --- a/include/linux/mm.h +++ b/include/linux/mm.h @@ -973,11 +973,21 @@ static inline struct mem_cgroup *page_memcg(struct page *page) { 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 --git a/mm/memcontrol.c b/mm/memcontrol.c index 3e8f9e5e9291..40dfca3ef4bb 100644 --- a/mm/memcontrol.c +++ b/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 @@ -943,39 +934,6 @@ static void invalidate_reclaim_iterators(struct mem_cgroup *dead_memcg) iter != NULL; \ 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 diff --git a/mm/workingset.c b/mm/workingset.c index 577277546d98..d7cc4bbd7e1b 100644 --- a/mm/workingset.c +++ b/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 *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(); } /* -- cgit v1.2.3