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

From: Con Kolivas
Date: Mon Dec 20 2004 - 03:24:53 EST

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.


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