[Devel] [RFC] how should we deal with dead memcgs' kmem caches?

[Vladimir Davydov]

21.04.2014 20:29, Christoph Lameter:
> On Sun, 20 Apr 2014, Vladimir Davydov wrote:
> 
>> * Way #1 - prevent dead kmem caches from caching slabs on free *
>>
>> We can modify sl[au]b implementation so that it won't cache any objects
>> on free if the kmem cache belongs to a dead memcg. Then it'd be enough
>> to drain per-cpu pools of all dead kmem caches on css offline - no new
>> slabs will be added there on further frees, and the last object will go
>> away along with the last slab.
> 
> You can call kmem_cache_shrink() to force slab allocators to drop cached
> objects after a free.

Yes, but the question is when and how often should we do that? Calling
it after each kfree would be an overkill, because there may be plenty of
objects in a dead cache. Calling it periodically or on vmpressure is the
first thing that springs to mind - that's covered by "way #2".

Thanks.