Date: Wed, 7 Apr 2004 19:01:26 -0700
From: Andrew Morton <akpm@osdl.org>
To: Benjamin Herrenschmidt <benh@kernel.crashing.org>
Cc: ak@suse.de, david@gibson.dropbear.id.au, linux-kernel@vger.kernel.org,
       anton@samba.org, paulus@samba.org, linuxppc64-dev@lists.linuxppc.org
Subject: Re: RFC: COW for hugepages
Message-Id: <20040407190126.06a9c38f.akpm@osdl.org>
In-Reply-To: <1081386710.1401.86.camel@gaston>
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	<1081386710.1401.86.camel@gaston>
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Benjamin Herrenschmidt <benh@kernel.crashing.org> wrote:
>
> 
> > Implementing this for ppc64 only is just wrong. Before you do this 
> > I would suggest to factor out the common code in the various hugetlbpage
> > implementations and then implement it in common code.
> 
> Have you actually looked at it and how huge pages are implemented
> on the various architectures ?
> 
> Honestly, I don't think we have any common abstraction on things
> like hugepte's etc... actually, archs aren't even required to use
> PTEs at all.
> 
> I don't see how we can make that code arch-neutral, at least not
> without a major redesign of the whole large pages mecanism.

I don't see much in the COW code which is ppc64-specific.  All the hardware
needs to do is to provide a way to make the big pages readonly.  With a bit
of an abstraction for the TLB manipulation in there it should be pretty
straightforward.

Certainly worth the attempt, no?
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