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Date: Tue, 4 Sep 2001 13:13:50 -0400
To: Rik van Riel <riel@conectiva.com.br>
Cc: Marcelo Tosatti <marcelo@conectiva.com.br>,
        Linus Torvalds <torvalds@transmeta.com>,
        Daniel Phillips <phillips@bonn-fries.net>,
        lkml <linux-kernel@vger.kernel.org>
Subject: Re: page_launder() on 2.4.9/10 issue
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From: Jan Harkes <jaharkes@cs.cmu.edu>
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On Tue, Sep 04, 2001 at 01:27:50PM -0300, Rik van Riel wrote:
> I've been working on a CPU and memory efficient reverse
> mapping patch for Linux, one which will allow us to do
> a bunch of optimisations for later on (infrastructure)
> and has as its short-term benefit the potential for
> better page aging.

Yes, I can see that using reverse mappings would be a way of correcting
the aging if you call page_age_up from try_to_swap_out, in which case
there probably needs to be a page_age_down on virtual mappings as well
to correctly balance things.

> It seems the balancing FreeBSD does (up aging +3, down
> aging -1, inactive list in LRU order as extra stage) is

One other observation, we should add anonymously allocated memory to the
active-list as soon as they are allocated in do_nopage. At the moment a
large part of memory is not aged at all until we start swapping things
out.

Jan