Re: [RFC] Optimization for use-once pages

From: Rik van Riel (
Date: Tue Jul 24 2001 - 12:04:28 EST

On Tue, 24 Jul 2001, Linus Torvalds wrote:

> Hey, this looks _really_ nice. I never liked the special-cases
> that you removed (drop_behind in particular), and I have to say
> that the new code looks a lot saner, even without your extensive
> description and timing analysis.

Fully agreed, drop_behind is an ugly hack. The sooner
it dies the happier I am ;)

> Please people, test this out extensively - I'd love to integrate
> it, but while it looks very sane I'd really like to hear of
> different peoples reactions to it under different loads.

The one thing which has always come up in LRU/k and 2Q
papers is that the "first reference" can really be a
series of references in a very short time.

Counting only the very first reference will fail if we
do eg. sequential IO with non-page aligned read() calls,
which doesn't look like it's too uncommon.

In order to prevent this from happening, either the system
counts all first references in a short timespan (complex to
implement) or it has the new pages on a special - small fixed
size - page list and all references to the page while on that
list are ignored.



Executive summary of a recent Microsoft press release:
   "we are concerned about the GNU General Public License (GPL)"

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This archive was generated by hypermail 2b29 : Tue Jul 31 2001 - 21:00:17 EST