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

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Message-ID: <20130419214709.GO3479@linux.vnet.ibm.com>
Date:	Fri, 19 Apr 2013 14:47:09 -0700
From:	"Paul E. McKenney" <paulmck@...ux.vnet.ibm.com>
To:	Kevin Hilman <khilman@...aro.org>
Cc:	linux-kernel@...r.kernel.org, mingo@...e.hu, laijs@...fujitsu.com,
	dipankar@...ibm.com, akpm@...ux-foundation.org,
	mathieu.desnoyers@...ymtl.ca, josh@...htriplett.org,
	niv@...ibm.com, tglx@...utronix.de, peterz@...radead.org,
	rostedt@...dmis.org, Valdis.Kletnieks@...edu, dhowells@...hat.com,
	edumazet@...gle.com, darren@...art.com, fweisbec@...il.com,
	sbw@....edu, Borislav Petkov <bp@...en8.de>,
	Arjan van de Ven <arjan@...ux.intel.com>,
	Christoph Lameter <cl@...ux.com>
Subject: Re: [PATCH documentation 1/2] nohz1: Add documentation.

On Fri, Apr 19, 2013 at 02:01:49PM -0700, Kevin Hilman wrote:
> "Paul E. McKenney" <paulmck@...ux.vnet.ibm.com> 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@...aro.org>

Added, thank you for the review and comments!

							Thanx, Paul

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