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

["Paul E. McKenney" <paulmck@linux.vnet.ibm.com>]

On Mon, Jul 01, 2013 at 06:19:10PM +0200, Andi Kleen wrote:
> > 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.
> 
> FWIW if you want useful testing you need to enable it by default
> (as part of NO_IDLE_HZ) anyways. Users will most likely pick
> whatever is "default" in Kconfig.

At this point in the process, I want testers who choose to test.  Hapless
victim testers come later.  Well, other than randconfig testers, but I
consider them to be voluntary hapless victims.  ;-)

> > > 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.
> 
> What performance part? 
> 
> Are you saying this adds so many checks to hot paths that normal runtime
> if() with a flag is too expensive?

I am saying that I don't know, and that I want to make it easy for people
to find out by comparing to the base configuration -- and for me to be
able to detect this from their .config file.

							Thanx, Paul