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

[Nick Piggin]

Hideo AOKI wrote:
> Nick Piggin wrote:
>
>
> > Andrew Morton wrote:
>
> [snip]
>
> > > 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?
>
>
> Hello,
>
> 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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