Use of function kmem_cache_shrink() in slab allocation

Question

While going through the slab allocation mechanism, I came across the following function.

int kmem_cache_shrink (struct kmem_cache *)

The description of this function can be found here.

The description only tells that this function is used to release as many slabs from the cache created. I think that the slabs which will have "empty" status will be only released.

Under what scenarios do we need this function?

Any inputs on this will be helpful.