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

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

[Paul E. McKenney]

On Thu, Apr 11, 2013 at 10:14:28AM -0700, Arjan van de Ven wrote:
> >+2.	Many architectures will place dyntick-idle CPUs into deep sleep
> >+	states, which further degrades from-idle transition latencies.
> >+
> I think this part should just be deleted.
> On x86, the deeper idle states are even used with non-tickless system (the break even times are
> quite a bit less than even 1 msec).
> I can't imagine that ARM is worse on this, at which point the statement above is highly dubious

Interesting point, and I freely admit that I don't have full knowledge
of the energy-consumption characteristics of all the architectures that
Linux supports.  Adding a few of the ARM guys on CC for their take,
plus linux-rt-users.

If there are no objections, I will delete point 2 above as Arjan suggests.

							Thanx, Paul

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

[Dipankar Sarma]

On Thu, Apr 11, 2013 at 11:27:27AM -0700, Paul E. McKenney wrote:
> On Thu, Apr 11, 2013 at 10:14:28AM -0700, Arjan van de Ven wrote:
> > >+2.	Many architectures will place dyntick-idle CPUs into deep sleep
> > >+	states, which further degrades from-idle transition latencies.
> > >+
> > I think this part should just be deleted.
> > On x86, the deeper idle states are even used with non-tickless system (the break even times are
> > quite a bit less than even 1 msec).
> > I can't imagine that ARM is worse on this, at which point the statement above is highly dubious
> 
> Interesting point, and I freely admit that I don't have full knowledge
> of the energy-consumption characteristics of all the architectures that
> Linux supports.  Adding a few of the ARM guys on CC for their take,
> plus linux-rt-users.
> 
> If there are no objections, I will delete point 2 above as Arjan suggests.

What Arjan said will also be true for Linux on Power systems. I am not
sure "many architectures" would be the right way to characterize it.

Thanks
Dipankar

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

[Paul E. McKenney]

On Fri, Apr 12, 2013 at 12:13:13AM +0530, Dipankar Sarma wrote:
> On Thu, Apr 11, 2013 at 11:27:27AM -0700, Paul E. McKenney wrote:
> > On Thu, Apr 11, 2013 at 10:14:28AM -0700, Arjan van de Ven wrote:
> > > >+2.	Many architectures will place dyntick-idle CPUs into deep sleep
> > > >+	states, which further degrades from-idle transition latencies.
> > > >+
> > > I think this part should just be deleted.
> > > On x86, the deeper idle states are even used with non-tickless system (the break even times are
> > > quite a bit less than even 1 msec).
> > > I can't imagine that ARM is worse on this, at which point the statement above is highly dubious
> > 
> > Interesting point, and I freely admit that I don't have full knowledge
> > of the energy-consumption characteristics of all the architectures that
> > Linux supports.  Adding a few of the ARM guys on CC for their take,
> > plus linux-rt-users.
> > 
> > If there are no objections, I will delete point 2 above as Arjan suggests.
> 
> What Arjan said will also be true for Linux on Power systems. I am not
> sure "many architectures" would be the right way to characterize it.

Very well, I count one non-objection to Arjan's suggestion.  ;-)

							Thanx, Paul