linux-kernel - Re: [PATCH 2/4] nohz: Print final full dynticks CPUs range on boot

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Message-ID: <20130329035124.GM3337@linux.vnet.ibm.com>
Date:	Thu, 28 Mar 2013 20:51:25 -0700
From:	"Paul E. McKenney" <paulmck@...ux.vnet.ibm.com>
To:	Paul Gortmaker <paul.gortmaker@...driver.com>
Cc:	Frederic Weisbecker <fweisbec@...il.com>,
	Ingo Molnar <mingo@...nel.org>,
	LKML <linux-kernel@...r.kernel.org>,
	Andrew Morton <akpm@...ux-foundation.org>,
	Chris Metcalf <cmetcalf@...era.com>,
	Christoph Lameter <cl@...ux.com>,
	Geoff Levand <geoff@...radead.org>,
	Gilad Ben Yossef <gilad@...yossef.com>,
	Hakan Akkan <hakanakkan@...il.com>,
	Kevin Hilman <khilman@...aro.org>,
	Li Zhong <zhong@...ux.vnet.ibm.com>,
	Namhyung Kim <namhyung.kim@....com>,
	Peter Zijlstra <peterz@...radead.org>,
	Steven Rostedt <rostedt@...dmis.org>,
	Thomas Gleixner <tglx@...utronix.de>
Subject: Re: [PATCH 2/4] nohz: Print final full dynticks CPUs range on boot

On Thu, Mar 28, 2013 at 10:08:23PM -0400, Paul Gortmaker wrote:
> [Re: [PATCH 2/4] nohz: Print final full dynticks CPUs range on boot] On 28/03/2013 (Thu 19:00) Paul E. McKenney wrote:
> 
> > On Fri, Mar 29, 2013 at 01:39:04AM +0100, Frederic Weisbecker wrote:
> > > 2013/3/29 Paul Gortmaker <paul.gortmaker@...driver.com>:
> > > > [Re: [PATCH 2/4] nohz: Print final full dynticks CPUs range on boot] On 28/03/2013 (Thu 08:40) Ingo Molnar wrote:
> > > >
> > > >>
> > > >> * Frederic Weisbecker <fweisbec@...il.com> wrote:
> > > >>
> > > >> > +   cpulist_scnprintf(nohz_ext_buf, sizeof(nohz_ext_buf), nohz_extended_mask);
> > > >> > +   pr_info("NO_HZ: Experimental full dynticks CPUs: %s.\n", nohz_ext_buf);
> > > >>
> > > >> I'd suggest removing the 'experimental' word. We are not sending anything
> > > >> experimental to Linus: we'll send something that is tested and that we
> > > >> expect to not break anything. (and which we'll fix if it does)
> > > >
> > > > In that case, should we vector a patch through PaulM to clobber these too?
> > > >
> > > > $ git grep xperiment |grep rcu
> > > > kernel/rcutree_plugin.h: printk(KERN_INFO "\tExperimental boot-time adjustment of leaf fanout to %d.\n", rcu_fanout_leaf);
> > 
> > This one has been this way for quite some time.  I must confess that I am
> > more inclined to remove this Kconfig option entirely than I am to remove
> > the "Experimental".  ;-)
> > 
> > > > kernel/rcutree_plugin.h: pr_info("\tExperimental no-CBs CPUs: %s.\n", nocb_buf);
> > > > kernel/rcutree_plugin.h: pr_info("\tExperimental polled no-CBs CPUs.\n");
> > > 
> > > Hehe, that's indeed what I inspired from ;-)
> > 
> > I guess we can rerun the earlier "how to mark Kconfig options as not
> > yet being ready for 100 million unsuspecting victims^Wusers.  ;-)
> 
> Perhaps consider "hiding" these kinds of choices behind CONFIG_EXPERT ?

We tried that with CONFIG_EXPERIMENTAL (or something like that), and
what happened was that all distros eventually enabled CONFIG_EXPERIMENTAL.

But if I was -really- serious about keeping the testing population down,
I would take Matthew Garret's advice and force a splat during boot-up.
So I now have a commit for 3.11 queued to remove the "Experimental"
from these strings, with your Reported-by.

							Thanx, Paul

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