Re: [PATCH RFC nohz_full 0/7] v2 Provide infrastructure forfull-system idle

[Paul E. McKenney]

On Mon, Jul 01, 2013 at 08:19:25AM -0700, Andi Kleen wrote:
> "Paul E. McKenney" <paulmck@xxxxxxxxxxxxxxxxxx> writes:
> >
> > The individual patches are as follows:
> >
> > 1.	Add a CONFIG_NO_HZ_FULL_SYSIDLE Kconfig parameter to enable
> > 	this feature.  Kernels built with CONFIG_NO_HZ_FULL_SYSIDLE=n
> > 	act exactly as they do today.
> 
> Is this extra CONFIG option really needed? RCU already has a bewildering
> variety of CONFIG options, and no idle CONFIG is also pretty complicated. 
> At some point noone will know how to configure kernels anymore if 
> these non trivial, complicated trade off CONFIGs keep spreading.
> 
> The facility sounds like a good thing in general. Just enable
> it implicitely with NO_HZ_SYSIDLE ? 

I am guessing that you want CONFIG_NO_HZ_FULL to implicitly enable
the sysidle code so that CONFIG_NO_HZ_FULL_SYSIDLE can be eliminated.
I will be happy to take that step, but only after I gain full confidence
in the correctness and performance of the sysidle code.

> If you want a switch for testing I would advise a sysctl or sysfs knob

This would work well for the correctness part, but not for the performance
part.

							Thanx, Paul

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