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

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Date:   Tue, 19 Dec 2017 17:53:36 -0800
From:   Matthew Wilcox <willy@...radead.org>
To:     "Paul E. McKenney" <paulmck@...ux.vnet.ibm.com>
Cc:     Jesper Dangaard Brouer <brouer@...hat.com>, rao.shoaib@...cle.com,
        linux-kernel@...r.kernel.org, linux-mm@...ck.org
Subject: Re: [PATCH] kfree_rcu() should use the new kfree_bulk() interface
 for freeing rcu structures

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.