netdev - Re: [MM PATCH V4.1 5/6] slub: support for bulk free with SLUB freelists

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Message-ID: <20151002124001.2c1d9d7d@redhat.com>
Date:	Fri, 2 Oct 2015 12:40:01 +0200
From:	Jesper Dangaard Brouer <brouer@...hat.com>
To:	Christoph Lameter <cl@...ux.com>
Cc:	Andrew Morton <akpm@...ux-foundation.org>, linux-mm@...ck.org,
	Alexander Duyck <alexander.duyck@...il.com>,
	Pekka Enberg <penberg@...nel.org>, netdev@...r.kernel.org,
	Joonsoo Kim <iamjoonsoo.kim@....com>,
	David Rientjes <rientjes@...gle.com>, brouer@...hat.com
Subject: Re: [MM PATCH V4.1 5/6] slub: support for bulk free with SLUB
 freelists

On Fri, 2 Oct 2015 05:10:02 -0500 (CDT)
Christoph Lameter <cl@...ux.com> wrote:

> On Fri, 2 Oct 2015, Jesper Dangaard Brouer wrote:
> 
> > Thus, I need introducing new code like this patch and at the same time
> > have to reduce the number of instruction-cache misses/usage.  In this
> > case we solve the problem by kmem_cache_free_bulk() not getting called
> > too often. Thus, +17 bytes will hopefully not matter too much... but on
> > the other hand we sort-of know that calling kmem_cache_free_bulk() will
> > cause icache misses.
> 
> Can we just drop the WARN/BUG here? Nothing untoward happens if size == 0
> right?

I think we crash if size == 0, as we deref p[--size] in build_detached_freelist().


(aside note: The code do handles if pointers in the p array are NULL)
-- 
Best regards,
  Jesper Dangaard Brouer
  MSc.CS, Principal Kernel Engineer at Red Hat
  Author of http://www.iptv-analyzer.org
  LinkedIn: http://www.linkedin.com/in/brouer
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