From mboxrd@z Thu Jan  1 00:00:00 1970
From: Mike Galbraith <umgwanakikbuti@gmail.com>
Subject: Re: [PATCH 0/6] support "dataplane" mode for nohz_full
Date: Tue, 12 May 2015 03:47:55 +0200
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Cc: Frederic Weisbecker <fweisbec@gmail.com>, Steven Rostedt <rostedt@goodmis.org>, Ingo Molnar <mingo@kernel.org>, Andrew Morton <akpm@linux-foundation.org>, Gilad Ben Yossef <giladb@ezchip.com>, Ingo Molnar <mingo@redhat.com>, Peter Zijlstra <peterz@infradead.org>, Rik van Riel <riel@redhat.com>, Tejun Heo <tj@kernel.org>, Thomas Gleixner <tglx@linutronix.de>, "Paul E. McKenney" <paulmck@linux.vnet.ibm.com>, Christoph Lameter <cl@linux.com>, "Srivatsa S. Bhat" <srivatsa.bhat@linux.vnet.ibm.com>, linux-doc@vger.kernel.org, linux-api@vger.kernel.org, linux-kernel@vger.kernel.org
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On Mon, 2015-05-11 at 15:25 -0400, Chris Metcalf wrote:
> On 05/11/2015 03:19 PM, Mike Galbraith wrote:
> > I really shouldn't have acked nohz_full -> isolcpus.  Beside the fact
> > that old static isolcpus was_supposed_  to crawl off and die, I know
> > beyond doubt that having isolated a cpu as well as you can definitely
> > does NOT imply that said cpu should become tickless.
> 
> True, at a high level, I agree that it would be better to have a
> top-level concept like Frederic's proposed ISOLATION that includes
> isolcpus and nohz_cpu (and other stuff as needed).
> 
> That said, what you wrote above is wrong; even with the patch you
> acked, setting isolcpus does not automatically turn on nohz_full for
> a given cpu.  The patch made it true the other way around: when
> you say nohz_full, you automatically get isolcpus on that cpu too.
> That does, at least, make sense for the semantics of nohz_full.

I didn't write that, I wrote nohz_full implies (spelled '->') isolcpus.
Yes, with nohz_full currently being static, the old allegedly dying but
also static isolcpus scheduler off switch is a convenient thing to wire
the nohz_full CPU SET (<- hint;) property to.

	-Mike