Date: Mon, 7 Nov 2005 15:35:38 -0800
From: William Lee Irwin III <wli@holomorphy.com>
To: Adam Litke <agl@us.ibm.com>
Cc: linux-mm@kvack.org, linux-kernel@vger.kernel.org,
       David Gibson <david@gibson.dropbear.id.au>, hugh@veritas.com,
       rohit.seth@intel.com, "Chen, Kenneth W" <kenneth.w.chen@intel.com>,
       akpm@osdl.org
Subject: Re: [RFC 2/2] Hugetlb COW
Message-ID: <20051107233538.GH29402@holomorphy.com>
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On Mon, Nov 07, 2005 at 03:38:53PM -0600, Adam Litke wrote:
> [RFC] COW for hugepages
> (Patch originally from David Gibson <dwg@au1.ibm.com>)
> This patch implements copy-on-write for hugepages, hence allowing
> MAP_PRIVATE mappings of hugetlbfs.
> This is chiefly useful for cases where we want to use hugepages
> "automatically" - that is to map hugepages without the knowledge of
> the code in the final application (either via kernel hooks, or with
> LD_PRELOAD).  We can use various heuristics to determine when
> hugepages might be a good idea, but changing the semantics of
> anonymous memory from MAP_PRIVATE to MAP_SHARED without the app's
> knowledge is clearly wrong.

I'll go check for architectures where page protections may be encoded
differently depending on the size of the translation, or whose code is
otherwise unprepared to cope with protection bits.

If you've done such checking already, I'd be much obliged to hear of it
(in fact, I'd much prefer you to have done so).


-- wli
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