[Cc Vladimir] On Wed 21-03-18 15:43:01, Shakeel Butt wrote: > With kmem cgroup support, high memcgs churn can leave behind a lot of > empty kmem_caches. Usually such kmem_caches will be destroyed when the > corresponding memcg gets released but the memcg release can be > arbitrarily delayed. These empty kmem_caches wastes cache_reaper's time. > So, the reaper should destroy such empty offlined kmem_caches. > > Signed-off-by: Shakeel Butt <[email protected]> > --- > mm/slab.c | 18 ++++++++++++++++-- > mm/slab.h | 15 +++++++++++++++ > mm/slab_common.c | 2 +- > 3 files changed, 32 insertions(+), 3 deletions(-) > > diff --git a/mm/slab.c b/mm/slab.c > index 66f2db98f026..9c174a799ffb 100644 > --- a/mm/slab.c > +++ b/mm/slab.c > @@ -4004,6 +4004,16 @@ static void drain_array(struct kmem_cache *cachep, > struct kmem_cache_node *n, > slabs_destroy(cachep, &list); > } > > +static bool is_slab_active(struct kmem_cache *cachep) > +{ > + int node; > + struct kmem_cache_node *n; > + > + for_each_kmem_cache_node(cachep, node, n) > + if (READ_ONCE(n->total_slabs) - n->free_slabs) > + return true; > + return false; > +} > /** > * cache_reap - Reclaim memory from caches. > * @w: work descriptor > @@ -4018,7 +4028,7 @@ static void drain_array(struct kmem_cache *cachep, > struct kmem_cache_node *n, > */ > static void cache_reap(struct work_struct *w) > { > - struct kmem_cache *searchp; > + struct kmem_cache *searchp, *tmp; > struct kmem_cache_node *n; > int node = numa_mem_id(); > struct delayed_work *work = to_delayed_work(w); > @@ -4027,7 +4037,7 @@ static void cache_reap(struct work_struct *w) > /* Give up. Setup the next iteration. */ > goto out; > > - list_for_each_entry(searchp, &slab_caches, list) { > + list_for_each_entry_safe(searchp, tmp, &slab_caches, list) { > check_irq_on(); > > /* > @@ -4061,6 +4071,10 @@ static void cache_reap(struct work_struct *w) > 5 * searchp->num - 1) / (5 * searchp->num)); > STATS_ADD_REAPED(searchp, freed); > } > + > + /* Eagerly delete inactive kmem_cache of an offlined memcg. */ > + if (!is_memcg_online(searchp) && !is_slab_active(searchp)) > + shutdown_cache(searchp); > next: > cond_resched(); > } > diff --git a/mm/slab.h b/mm/slab.h > index e8981e811c45..e911b10efae7 100644 > --- a/mm/slab.h > +++ b/mm/slab.h > @@ -166,6 +166,7 @@ static inline slab_flags_t kmem_cache_flags(unsigned int > object_size, > SLAB_TEMPORARY | \ > SLAB_ACCOUNT) > > +int shutdown_cache(struct kmem_cache *s); > int __kmem_cache_shutdown(struct kmem_cache *); > void __kmem_cache_release(struct kmem_cache *); > int __kmem_cache_shrink(struct kmem_cache *); > @@ -290,6 +291,15 @@ static __always_inline void memcg_uncharge_slab(struct > page *page, int order, > memcg_kmem_uncharge(page, order); > } > > +static __always_inline bool is_memcg_online(struct kmem_cache *s) > +{ > + if (!memcg_kmem_enabled()) > + return true; > + if (is_root_cache(s)) > + return true; > + return mem_cgroup_online(s->memcg_params.memcg); > +} > + > extern void slab_init_memcg_params(struct kmem_cache *); > extern void memcg_link_cache(struct kmem_cache *s); > extern void slab_deactivate_memcg_cache_rcu_sched(struct kmem_cache *s, > @@ -342,6 +352,11 @@ static inline void memcg_uncharge_slab(struct page > *page, int order, > { > } > > +static inline bool is_memcg_online(struct kmem_cache *s) > +{ > + return true; > +} > + > static inline void slab_init_memcg_params(struct kmem_cache *s) > { > } > diff --git a/mm/slab_common.c b/mm/slab_common.c > index 61ab2ca8bea7..d197e878636b 100644 > --- a/mm/slab_common.c > +++ b/mm/slab_common.c > @@ -573,7 +573,7 @@ static void slab_caches_to_rcu_destroy_workfn(struct > work_struct *work) > } > } > > -static int shutdown_cache(struct kmem_cache *s) > +int shutdown_cache(struct kmem_cache *s) > { > /* free asan quarantined objects */ > kasan_cache_shutdown(s); > -- > 2.17.0.rc0.231.g781580f067-goog
-- Michal Hocko SUSE Labs
