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To: Cyrill Gorcunov <gorcunov@gmail.com>
Cc: Christoph Lameter <cl@linux-foundation.org>,
       Pekka Enberg <penberg@cs.helsinki.fi>,
       LKML <linux-kernel@vger.kernel.org>,
       Andrew Morton <akpm@linux-foundation.org>
Subject: Re: mm: slab - __cache_alloc NULL prefetch fix
In-Reply-To: Your message of "Thu, 20 Nov 2008 19:44:00 +0300."
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From: Valdis.Kletnieks@vt.edu
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Date: Thu, 20 Nov 2008 14:58:28 -0500
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On Thu, 20 Nov 2008 19:44:00 +0300, Cyrill Gorcunov said:

> -	prefetchw(objp);
>  
> -	if (likely(objp))
> +	if (likely(objp)) {
> +		prefetchw(objp);
>  		kmemcheck_slab_alloc(cachep, flags, objp, obj_size(cachep));
> +	}

Although it probably makes sense to not bother prefetching NULL, I also
need to wonder how useful it is to prefetch something that we then
turn around and dereference in the very next line of code.

Maybe we should just lose the prefetch entirely?

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