Re: why swap at all?

[Nick Piggin]

Tom Felker wrote:
> On Wednesday 26 May 2004 7:37 am, Matthias Schniedermeyer wrote:
>
>
> > program to kernel: "i read ONCE though this file caching not useful".
>
>
> Very true.  The system is based on the assumption that just-used pages are 
> more useful that older pages, and it slows when this isn't true.  We need 
> ways to tell the kernel whether the assumption holds.

A streaming flag is great, but we usually do OK without it. There
is a "used once" heuristic that often gets it right as far as I
know. Basically, new pages that are only used once put almost zero
pressure on the rest of the memory.

It has a few corner cases where it breaks down. Hopefully they can
be improved...
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