Re: [PATCH -mm 7/8] slub: make dead caches discard free slabs immediately

[Christoph Lameter]

On Fri, 30 May 2014, Vladimir Davydov wrote:

> (3) is a bit more difficult, because slabs are added to per-cpu partial
> lists lock-less. Fortunately, we only have to handle the __slab_free
> case, because, as there shouldn't be any allocation requests dispatched
> to a dead memcg cache, get_partial_node() should never be called. In
> __slab_free we use cmpxchg to modify kmem_cache_cpu->partial (see
> put_cpu_partial) so that setting ->partial to a special value, which
> will make put_cpu_partial bail out, will do the trick.
>
> Note, this shouldn't affect performance, because keeping empty slabs on
> per node lists as well as using per cpu partials are only worthwhile if
> the cache is used for allocations, which isn't the case for dead caches.

This all sounds pretty good to me but we still have some pretty extensive
modifications that I would rather avoid.

In put_cpu_partial you can simply check that the memcg is dead right? This
would avoid all the other modifications I would think and will not require
a special value for the per cpu partial pointer.
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