diff --git a/mm/memcontrol.c b/mm/memcontrol.c index 15e6fb5d56a7..ae12fdd4bc0d 100644 --- a/mm/memcontrol.c +++ b/mm/memcontrol.c @@ -103,11 +103,6 @@ static bool do_memsw_account(void) return !cgroup_subsys_on_dfl(memory_cgrp_subsys) && !cgroup_memory_noswap; } -/* memcg and lruvec stats flushing */ -static void flush_memcg_stats_dwork(struct work_struct *w); -static DECLARE_DEFERRABLE_WORK(stats_flush_dwork, flush_memcg_stats_dwork); -static DEFINE_SPINLOCK(stats_flush_lock); - #define THRESHOLDS_EVENTS_TARGET 128 #define SOFTLIMIT_EVENTS_TARGET 1024 @@ -635,6 +630,56 @@ mem_cgroup_largest_soft_limit_node(struct mem_cgroup_tree_per_node *mctz) return mz; } +/* + * memcg and lruvec stats flushing + * + * Many codepaths leading to stats update or read are performance sensitive and + * adding stats flushing in such codepaths is not desirable. So, to optimize the + * flushing the kernel does: + * + * 1) Periodically and asynchronously flush the stats every 2 seconds to not let + * rstat update tree grow unbounded. + * + * 2) Flush the stats synchronously on reader side only when there are more than + * (MEMCG_CHARGE_BATCH * nr_cpus) update events. Though this optimization + * will let stats be out of sync by atmost (MEMCG_CHARGE_BATCH * nr_cpus) but + * only for 2 seconds due to (1). + */ +static void flush_memcg_stats_dwork(struct work_struct *w); +static DECLARE_DEFERRABLE_WORK(stats_flush_dwork, flush_memcg_stats_dwork); +static DEFINE_SPINLOCK(stats_flush_lock); +static DEFINE_PER_CPU(unsigned int, stats_updates); +static atomic_t stats_flush_threshold = ATOMIC_INIT(0); + +static inline void memcg_rstat_updated(struct mem_cgroup *memcg) +{ + cgroup_rstat_updated(memcg->css.cgroup, smp_processor_id()); + if (!(__this_cpu_inc_return(stats_updates) % MEMCG_CHARGE_BATCH)) + atomic_inc(&stats_flush_threshold); +} + +static void __mem_cgroup_flush_stats(void) +{ + if (!spin_trylock(&stats_flush_lock)) + return; + + cgroup_rstat_flush_irqsafe(root_mem_cgroup->css.cgroup); + atomic_set(&stats_flush_threshold, 0); + spin_unlock(&stats_flush_lock); +} + +void mem_cgroup_flush_stats(void) +{ + if (atomic_read(&stats_flush_threshold) > num_online_cpus()) + __mem_cgroup_flush_stats(); +} + +static void flush_memcg_stats_dwork(struct work_struct *w) +{ + mem_cgroup_flush_stats(); + queue_delayed_work(system_unbound_wq, &stats_flush_dwork, 2UL*HZ); +} + /** * __mod_memcg_state - update cgroup memory statistics * @memcg: the memory cgroup @@ -647,7 +692,7 @@ void __mod_memcg_state(struct mem_cgroup *memcg, int idx, int val) return; __this_cpu_add(memcg->vmstats_percpu->state[idx], val); - cgroup_rstat_updated(memcg->css.cgroup, smp_processor_id()); + memcg_rstat_updated(memcg); } /* idx can be of type enum memcg_stat_item or node_stat_item. */ @@ -675,10 +720,12 @@ void __mod_memcg_lruvec_state(struct lruvec *lruvec, enum node_stat_item idx, memcg = pn->memcg; /* Update memcg */ - __mod_memcg_state(memcg, idx, val); + __this_cpu_add(memcg->vmstats_percpu->state[idx], val); /* Update lruvec */ __this_cpu_add(pn->lruvec_stats_percpu->state[idx], val); + + memcg_rstat_updated(memcg); } /** @@ -780,7 +827,7 @@ void __count_memcg_events(struct mem_cgroup *memcg, enum vm_event_item idx, return; __this_cpu_add(memcg->vmstats_percpu->events[idx], count); - cgroup_rstat_updated(memcg->css.cgroup, smp_processor_id()); + memcg_rstat_updated(memcg); } static unsigned long memcg_events(struct mem_cgroup *memcg, int event) @@ -5341,21 +5388,6 @@ static void mem_cgroup_css_reset(struct cgroup_subsys_state *css) memcg_wb_domain_size_changed(memcg); } -void mem_cgroup_flush_stats(void) -{ - if (!spin_trylock(&stats_flush_lock)) - return; - - cgroup_rstat_flush_irqsafe(root_mem_cgroup->css.cgroup); - spin_unlock(&stats_flush_lock); -} - -static void flush_memcg_stats_dwork(struct work_struct *w) -{ - mem_cgroup_flush_stats(); - queue_delayed_work(system_unbound_wq, &stats_flush_dwork, 2UL*HZ); -} - static void mem_cgroup_css_rstat_flush(struct cgroup_subsys_state *css, int cpu) { struct mem_cgroup *memcg = mem_cgroup_from_css(css);