netdev - Re: [PATCH mm] slab: implement bulking for SLAB allocator

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Message-ID: <20150908175451.2ce83a0b@redhat.com>
Date:	Tue, 8 Sep 2015 17:54:51 +0200
From:	Jesper Dangaard Brouer <brouer@...hat.com>
To:	Christoph Lameter <cl@...ux.com>
Cc:	iamjoonsoo.kim@....com, akpm@...ux-foundation.org,
	linux-mm@...ck.org, netdev@...r.kernel.org, brouer@...hat.com
Subject: Re: [PATCH mm] slab: implement bulking for SLAB allocator

On Tue, 8 Sep 2015 10:22:32 -0500 (CDT)
Christoph Lameter <cl@...ux.com> wrote:

> On Tue, 8 Sep 2015, Jesper Dangaard Brouer wrote:
> 
> > Also notice how well bulking maintains the performance when the bulk
> > size increases (which is a soar spot for the slub allocator).
> 
> Well you are not actually completing the free action in SLAB. This is
> simply queueing the item to be freed later. Also was this test done on a
> NUMA system? Alien caches at some point come into the picture.

This test was a single CPU benchmark with no congestion or concurrency.
But the code was compiled with CONFIG_NUMA=y.

I don't know the slAb code very well, but the kmem_cache_node->list_lock
looks like a scalability issue.  I guess that is what you are referring
to ;-)

-- 
Best regards,
  Jesper Dangaard Brouer
  MSc.CS, Sr. Network Kernel Developer at Red Hat
  Author of http://www.iptv-analyzer.org
  LinkedIn: http://www.linkedin.com/in/brouer
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