Re: cp file /dev/zero <-> cache [was Re: increasing page size]

Rik van Riel (H.H.vanRiel@phys.uu.nl)
Tue, 7 Jul 1998 17:54:46 +0200 (CEST)

On Tue, 7 Jul 1998, Stephen C. Tweedie wrote:
> On Mon, 6 Jul 1998 21:28:42 +0200 (CEST), Andrea Arcangeli
> <arcangeli@mbox.queen.it> said:
>
> > It would be nice if it would be swapped out _only_ pages that are not used
> > in the past half an hour. If kswapd would run in such way I would thank
> > you a lot instead of being irritate ;-).
>
> ?? Some people will want to keep anything used within the last half
> hour; in other cases, 5 minutes idle should qualify for a swapout. On
> the compilation benchmarks I run on 6MB machines, any page not used
> within the past 10 seconds or so should be history!

There's a good compromize between balancing per-page
and per-process. We can simply declare the last X
(say 8) pages of a process holy unless that process
has slept for more than Y (say 5) seconds.

As a temporary measure, you can tune swapctl to
have an age_cluster_fract of 128 and an
age_cluster_min of 0; this will leave the 8 last
pages of an app in memory, whatever happens...

Rik.
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