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Date: Mon, 28 Jan 2002 16:01:41 -0200 (BRST)
From: Rik van Riel <riel@conectiva.com.br>
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To: Linus Torvalds <torvalds@transmeta.com>
Cc: Josh MacDonald <jmacd@CS.Berkeley.EDU>, <linux-kernel@vger.kernel.org>,
        <reiserfs-list@namesys.com>, <reiserfs-dev@namesys.com>
Subject: Re: Note describing poor dcache utilization under high memory pressure
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On Mon, 28 Jan 2002, Linus Torvalds wrote:

> I am, for example, very interested to see if Rik can get the overhead of
> the rmap stuff down low enough that it's not a noticeable hit under
> non-VM-pressure. I'm looking at the issue of doing COW on the page tables
> (which really is a separate issue), because it might make it more
> palatable to go with the rmap approach.

I'd be interested to know exactly how much overhead -rmap is
causing for both page faults and fork   (but I'm sure one of
the regular benchmarkers can figure that one out while I fix
the RSS limit stuff ;))

About page table COW ... I've thought about it a lot and it
wouldn't surprise me if the 4 MB granularity of page tables
is too large to be of a real benefit since the classic path
of fork+exec would _still_ get all 3 page tables of the
typical process copied.

OTOH, it wouldn't surprise me at all if it was a win ;))

kind 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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