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Date:      Wed, 01 Nov 2000 22:31:40 -0800
From:      David Greenman <dg@root.com>
To:        janb@cs.utep.edu
Cc:        freebsd-current@FreeBSD.ORG
Subject:   Re: current paging strategy 
Message-ID:  <200011020631.WAA12676@implode.root.com>
In-Reply-To: Your message of "Wed, 01 Nov 2000 21:34:25 MST." <Pine.GSO.4.05.10011012132490.20876-100000@gecko> 

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>What paging strategy does FreeBSD currently use? Is it LRU or some
>approximation to it? How much memory does this strategy take up in its
>current implementation?

   It's probably nothing like anything you've heard of before. It's closest
to LOU (least often used). We look at the page's reference flag and
increment/decrement a counter depending on it. The rate that we look at
the reference flag is also roughly proportional to the rate at which new
pages are needed. This algorithm has proven to be extremely effective and
does much better than simple LRU.

-DG

David Greenman
Co-founder, The FreeBSD Project - http://www.freebsd.org
President, TeraSolutions, Inc. - http://www.terasolutions.com
Pave the road of life with opportunities.


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