Re: Linux VM design

Daniel Phillips (phillips@bonn-fries.net)
Mon, 24 Sep 2001 20:37:17 +0200

On September 24, 2001 11:36 am, VDA wrote:
> Daniel Phillips <phillips@bonn-fries.net> wrote:
> DP> The arguments in support of aging over LRU that I'm aware of are:
>
> DP> - incrementing an age is more efficient than resetting several LRU
> DP> list links
> DP> - also captures some frequency-of-use information
>
> Of what use this info can be? If one page is accessed 100 times/second
> and other one once in 10 seconds, they both have to stay in RAM.
> VM should take 'time since last access' into account whan deciding
> which page to swap out, not how often it was referenced.

You might want to have a look at this:

http://archi.snu.ac.kr/jhkim/seminar/96-004.ps
(lrfu algorithm)

To tell the truth, I don't really see why the frequency information is all
that useful either. Rik suggested it's good for streaming IO but we already
have effective means of dealing with that that don't rely on any frequency
information.

So the list of reasons why aging is good is looking really short.

--
Daniel
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