Re: [PATCH documentation 1/2] nohz1: Add documentation.

From: Paul E. McKenney
Date: Fri Apr 19 2013 - 17:47:29 EST


On Fri, Apr 19, 2013 at 02:01:49PM -0700, Kevin Hilman wrote:
> "Paul E. McKenney" <paulmck@xxxxxxxxxxxxxxxxxx> writes:
>
> > +KNOWN ISSUES
>
> [...]
>
> > +o Unless all CPUs are idle, at least one CPU must keep the
> > + scheduling-clock interrupt going in order to support accurate
> > + timekeeping.
>
> At least with the implementation I'm using (Frederic's 3.9-nohz1
> branch), at least one CPU is forced to stay out of dyntick-idle
> *always*, even if all CPUs are idle.
>
> IMO, this is important to list as a known issue since this will have
> its own power implications when the system is mostly idle.

Good point! I added the following at the end of the known issues:

o If there are adaptive-ticks CPUs, there will be at least one
CPU keeping the scheduling-clock interrupt going, even if all
CPUs are otherwise idle.

> Otherwise, document looks great.
>
> Reviewed-by: Kevin Hilman <khilman@xxxxxxxxxx>

Added, thank you for the review and comments!

Thanx, Paul

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