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

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Message-ID: <20130411184313.GH22229@in.ibm.com>
Date:	Fri, 12 Apr 2013 00:13:13 +0530
From:	Dipankar Sarma <dipankar@...ibm.com>
To:	"Paul E. McKenney" <paulmck@...ux.vnet.ibm.com>
Cc:	Arjan van de Ven <arjan@...ux.intel.com>,
	linux-kernel@...r.kernel.org, mingo@...e.hu, laijs@...fujitsu.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>,
	Kevin Hilman <khilman@...aro.org>,
	Christoph Lameter <cl@...ux.com>, arnd@...db.de,
	Robin.Randhawa@....com, linux-rt-users@...r.kernel.org
Subject: Re: [PATCH documentation 1/2] nohz1: Add documentation.

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

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