From: William Lee Irwin III <wli@holomorphy.com>
To: Andrew Morton <akpm@osdl.org>
Cc: Albert Cahalan <albert@users.sourceforge.net>,
linux-kernel@vger.kernel.org, riel@redhat.com
Subject: Re: pte_addr_t size reduction for 64 GB case?
Date: Wed, 19 May 2004 01:08:45 -0700 [thread overview]
Message-ID: <20040519080845.GF1223@holomorphy.com> (raw)
In-Reply-To: <20040519004424.72f5eb9e.akpm@osdl.org>
Albert Cahalan <albert@users.sourceforge.net> wrote:
>> When handling 64 GB on i386, pte_addr_t really only
>> needs 33 bits to find the PTE. It sure doesn't need
>> the full 64 bits it is using.
On Wed, May 19, 2004 at 12:44:24AM -0700, Andrew Morton wrote:
> yup.
Albert Cahalan <albert@users.sourceforge.net> wrote:
>> How about cheating a bit? If the pte_addr_t only had
>> the high 32 bits of the 36-bit pointer, it would point
>> to a pair of the 8-byte PTEs in a 16-byte chunk of RAM.
>> Then simply examine the PTEs to see which one is the
>> correct one.
On Wed, May 19, 2004 at 12:44:24AM -0700, Andrew Morton wrote:
> They might both map the same page. It could overflow into page->flags.
An overflow area for the 33rd bits in pte_chains is another idea. A
CONFIG_HIGHMEM32G is another. But Hugh's and/or Andrea's code sounds
nicer than either of those. It doesn't get smaller than 0.
-- wli
next prev parent reply other threads:[~2004-05-19 8:08 UTC|newest]
Thread overview: 4+ messages / expand[flat|nested] mbox.gz Atom feed top
2004-05-19 4:42 pte_addr_t size reduction for 64 GB case? Albert Cahalan
2004-05-19 7:44 ` Andrew Morton
2004-05-19 8:08 ` William Lee Irwin III [this message]
2004-05-19 11:18 ` Rik van Riel
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