On Sun, Oct 08, 2017 at 01:56:08AM +0100, Al Viro wrote: > What's more, we need to be careful about resize vs. drain. Right now it's > on list_lrus_mutex, but if we drop that around actual resize of an individual > list_lru, we'll need something else. Would there be any problem if we > took memcg_cache_ids_sem shared in memcg_offline_kmem()? > > The first problem is not fatal - we can e.g. use the sign of the field used > to store the number of ->memcg_lrus elements (i.e. stashed value of > memcg_nr_cache_ids at allocation or last resize) to indicate that actual > freeing is left for resizer... Ugh. That spinlock would have to be held over too much work, or bounced back and forth a lot on memcg shutdowns ;-/ Gets especially nasty if we want list_lru_destroy() callable from rcu callbacks. Oh, well... I still suspect that locking there is too heavy, but it looks like I don't have a better replacement. What are the realistic numbers of memcg on a big system?
