Re: 2.6.10-rc3: kswapd eats CPU on start of memory-eating task

[Con Kolivas]

Nick Piggin wrote:
> Andrew Morton wrote:
>
> > Voluspa <lista4@xxxxxxxxx> wrote:
> >
> > > Would be nice though if someone else could verify...
> >
> >
> >
> > Well I'd love to, but afaik the only workloads which we currently know of
> > involve complex userspace apps which I have no experience running.
> >
> > Did anyone come up with a simple step-by-step procedure for 
> > reproducing the
> > problem?  It would be good if someone could do this, because I don't 
> > think
> > we understand the root cause yet?
>
> I admit to generally being in the same boat as you with respect to
> running complex userspace apps.
>
> However, based on this and other scattered reports, I'd say it seems
> quite likely that token based thrashing control is the culprit. Based
> on the cost/benefit, I wonder if we should disable TBTC by default for
> 2.6.10, rather than trying to fix it, and try again for 2.6.11?
>
> Rik? Andrew?
>
> Also, it would be nice to have a sysctl to *completely* disable TBTC,
> that would make testing easier.

Logistically what makes sense is if a timeout of 0 is used as a test 
that completely disables it (avoids another sysctl too). In time for 
2.6.10 we should disable it by default until the regressions are better 
understood. Tuning it into a useful "on" position can happen later and I 
suspect requires more code.

Con

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