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Date: Wed, 16 Jan 2002 17:34:26 -0200 (BRST)
From: Rik van Riel <riel@conectiva.com.br>
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To: Linus Torvalds <torvalds@transmeta.com>
Cc: Andrea Arcangeli <andrea@suse.de>, <linux-kernel@vger.kernel.org>
Subject: Re: pte-highmem-5
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On Wed, 16 Jan 2002, Linus Torvalds wrote:

>  - do the highmem pte bouncing only for CONFIG_X86_PAE: with less then 4GB
>    of RAM this doesn't seem to matter all that much (rule of thumb: we
>    need about 1% of memory for page tables).

Actually, with 100 processes mapping a 1 GB area of shared
memory, you'll need about 100 MB of page tables or 10% of
the SHM segment. This rises even further with PAE and/or
more processes.

The page table cost for heavily shared memory segments is
really getting out of hand, IMHO ... it might be worth it
to set aside a separate memory zone and use 4 MB pages for
the SHM segment.

regards,

Rik
-- 
"Linux holds advantages over the single-vendor commercial OS"
    -- Microsoft's "Competing with Linux" document

http://www.surriel.com/		http://distro.conectiva.com/

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