Re: 'autogroup' sched code KILLING responsiveness

[Andreas Mohr <andi@lisas.de>]

> Christian, Michael, can you confirm that this and the second patch fixes the 
> interactivity bug for you? If yes then i'd like to apply and send this fix to Linus 
> ASAP.
> 
> Thanks,
> 
> 	Ingo

I'm currently running with autogroup enabled for the first time,
on Athlon XP -rc2 with _first patch only_ applied (saw second part too late),
and it appears to be working fine with some stress tests added
(multi-app benchmark, while... true, yes etc.).
Interestingly I had chosen to DISABLE the cgroup part of the scheduler
several months ago since it was slower than non-cgroup by quite some margin.


One should perhaps consider this issue to be evidence of a notable lack
of (possibly automated) test/usage coverage of UP configs
(together with the recent build error on UP that was discovered
once hitting -rc1 only, and not earlier!).


For this particular fix, perhaps the 0 vs. tg->shares change could be
followed up by a WARN_ON_ONCE() in some more internal non-hotpath function
if such a check is feasible in the current case.

Thanks,

Andreas Mohr