Re: [PATCH] kfree_rcu() should use the new kfree_bulk() interface for freeing rcu structures

[Matthew Wilcox]

On Tue, Dec 19, 2017 at 04:20:51PM -0800, Paul E. McKenney wrote:
> If we are going to make this sort of change, we should do so in a way
> that allows the slab code to actually do the optimizations that might
> make this sort of thing worthwhile.  After all, if the main goal was small
> code size, the best approach is to drop kfree_bulk() and get on with life
> in the usual fashion.
> 
> I would prefer to believe that something like kfree_bulk() can help,
> and if that is the case, we should give it a chance to do things like
> group kfree_rcu() requests by destination slab and soforth, allowing
> batching optimizations that might provide more significant increases
> in performance.  Furthermore, having this in slab opens the door to
> slab taking emergency action when memory is low.

kfree_bulk does sort by destination slab; look at build_detached_freelist.