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

From: Nick Piggin
Date: Mon Dec 20 2004 - 19:02:23 EST

Hideo AOKI wrote:
Nick Piggin wrote:

Andrew Morton wrote:


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?


I imagine that the issue might occur when only one process holds almost all memory and has swap token too long time.

However, TBTC has a good effect in my workload. So, I think that it is better to keep VM tunable using TBTC.
It may be a good idea to set 0 to default swap_token_timeout until we find the root cause.

Yes, with Con's patch to have TBTC turned off when swap_token_timeout
is set to zero. It causes unacceptable regressions, so that is the
best way to go.

It would be great to get it fixed, but I would be worried about putting
in new patches for it now, right before 2.6.10.
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