On Thu, May 10, 2018 at 12:52:18PM +0300, Kirill Tkhai wrote: > The patch introduces shrinker::id number, which is used to enumerate > memcg-aware shrinkers. The number start from 0, and the code tries > to maintain it as small as possible. > > This will be used as to represent a memcg-aware shrinkers in memcg > shrinkers map. > > Since all memcg-aware shrinkers are based on list_lru, which is per-memcg > in case of !SLOB only, the new functionality will be under MEMCG && !SLOB > ifdef (symlinked to CONFIG_MEMCG_SHRINKER). Using MEMCG && !SLOB instead of introducing a new config option was done deliberately, see: http://lkml.kernel.org/r/20151210202244.GA4809@xxxxxxxxxxx I guess, this doesn't work well any more, as there are more and more parts depending on kmem accounting, like shrinkers. If you really want to introduce a new option, I think you should call it CONFIG_MEMCG_KMEM and use it consistently throughout the code instead of MEMCG && !SLOB. And this should be done in a separate patch. > diff --git a/fs/super.c b/fs/super.c > index 122c402049a2..16c153d2f4f1 100644 > --- a/fs/super.c > +++ b/fs/super.c > @@ -248,6 +248,9 @@ static struct super_block *alloc_super(struct file_system_type *type, int flags, > s->s_time_gran = 1000000000; > s->cleancache_poolid = CLEANCACHE_NO_POOL; > > +#ifdef CONFIG_MEMCG_SHRINKER > + s->s_shrink.id = -1; > +#endif No point doing that - you are going to overwrite the id anyway in prealloc_shrinker(). > s->s_shrink.seeks = DEFAULT_SEEKS; > s->s_shrink.scan_objects = super_cache_scan; > s->s_shrink.count_objects = super_cache_count; > diff --git a/mm/vmscan.c b/mm/vmscan.c > index 10c8a38c5eef..d691beac1048 100644 > --- a/mm/vmscan.c > +++ b/mm/vmscan.c > @@ -169,6 +169,47 @@ unsigned long vm_total_pages; > static LIST_HEAD(shrinker_list); > static DECLARE_RWSEM(shrinker_rwsem); > > +#ifdef CONFIG_MEMCG_SHRINKER > +static DEFINE_IDR(shrinker_idr); > + > +static int prealloc_memcg_shrinker(struct shrinker *shrinker) > +{ > + int id, ret; > + > + down_write(&shrinker_rwsem); > + ret = id = idr_alloc(&shrinker_idr, shrinker, 0, 0, GFP_KERNEL); > + if (ret < 0) > + goto unlock; > + shrinker->id = id; > + ret = 0; > +unlock: > + up_write(&shrinker_rwsem); > + return ret; > +} > + > +static void del_memcg_shrinker(struct shrinker *shrinker) Nit: IMO unregister_memcg_shrinker() would be a better name as it matches unregister_shrinker(), just like prealloc_memcg_shrinker() matches prealloc_shrinker(). > +{ > + int id = shrinker->id; > + > + if (id < 0) > + return; Nit: I think this should be BUG_ON(id >= 0) as this function is only called for memcg-aware shrinkers AFAICS. > + > + down_write(&shrinker_rwsem); > + idr_remove(&shrinker_idr, id); > + up_write(&shrinker_rwsem); > + shrinker->id = -1; > +}
