On Mon, 19 May 2014, Vladimir Davydov wrote:

3) Per cpu partial slabs. We can disable this feature for dead caches by
adding appropriate check to kmem_cache_has_cpu_partial.

There is already a s->cpu_partial number in kmem_cache. If that is zero
then no partial cpu slabs should be kept.

So far, everything looks very simple - it seems we don't have to modify
__slab_free at all if we follow the instruction above.

However, there is one thing regarding preemptable kernels. The problem
is after forbidding the cache store free slabs in per-cpu/node partial
lists by setting min_partial=0 and kmem_cache_has_cpu_partial=false
(i.e. marking the cache as dead), we have to make sure that all frees
that saw the cache as alive are over, otherwise they can occasionally
add a free slab to a per-cpu/node partial list *after* the cache was
marked dead. For instance,

Ok then lets switch off preeempt there? Preemption is not supported by
most distribution and so will have the least impact.

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