Hi Christoph,

15.04.2014 19:17, Christoph Lameter:
On Tue, 15 Apr 2014, Vladimir Davydov wrote:

2) When freeing an object of a dead memcg cache, initiate thorough check
if the cache is really empty and destroy it then. That could be
implemented by poking the reaping thread on kfree, and actually does not
require the schedule_work in memcg_release_pages IMO.

There is already logic in both slub and slab that does that on cache
close.

Yeah, but here the question is when we should close caches left after memcg offline. Obviously we should do it after all objects of such a cache have gone, but when exactly? Do it immediately after the last kfree (have to count objects per cache then AFAIU) or may be check periodically (or on vmpressure) that the cache is empty by issuing kmem_cache_shrink and looking if memcg_params::nr_pages = 0?

Thanks.
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