add enable-cache-prefetch option

add enable-cache-prefetch option

OK. here is the work to clear all cache prefetch. Please review it. 3x

On Tue, Sep 21, 2010 at 11:36:30PM +0800, Soeren Sandmann wrote:
> Liu Xinyun <xinyun.liu@intel.com> writes:
>
> >    This patch is to add a new configuration option: enable-cache-prefetch,
> > which is default yes.
> >
> >    Here is a link which talks on cache issue.
> >    http://lists.freedesktop.org/archives/pixman/2010-June/000218.html
> >
> >    When disable it on Atom CPU(configured with --enable-cache-prefetch=no),
> > it will have a little performance gain. Here is the patch.
>
> I think the cache prefetch code should just be deleted outright. No
> benchmarks that I'm aware of show it to be an improvement.
>
>
> Thanks,
> Soren

>From bca2192ef524bcae4eea84d0ffed9e8c4855675f Mon Sep 17 00:00:00 2001
From: Liu Xinyun <xinyun.liu@intel.com>
Date: Wed, 22 Sep 2010 00:11:56 +0800
Subject: [PATCH] remove cache prefetch