Date: Wed, 7 Apr 2004 14:34:47 +0200
From: Andi Kleen <ak@suse.de>
To: David Gibson <david@gibson.dropbear.id.au>
Cc: akpm@osdl.org, linux-kernel@vger.kernel.org, benh@kernel.crashing.org,
       anton@samba.org, paulus@samba.org, linuxppc64-dev@lists.linuxppc.org
Subject: Re: RFC: COW for hugepages
Message-Id: <20040407143447.4d8f08af.ak@suse.de>
In-Reply-To: <20040407074239.GG18264@zax>
References: <20040407074239.GG18264@zax>
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On Wed, 7 Apr 2004 17:42:39 +1000
David Gibson <david@gibson.dropbear.id.au> wrote:

> Currently the kernel does not implement copy-on-write for huge pages -
> in fact any sort of page fault on a hugepage results in a SIGBUS.
> This means that hugepages *always* have MAP_SHARED semantics, even if
> MAP_PRIVATE is requested, and in particular that they are always
> shared across a fork().  Particularly when using hugetlbfs as just a
> source of quasi-anonymous memory, those are rather strange semantics.

[...]

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.

-Andi
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