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

[Nick Piggin <nickpiggin@yahoo.com.au>]

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.