linux-kernel - Re: [GIT RFC PULL rcu/urgent] Prevent Kconfig from asking pointless questions

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Date:	Mon, 20 Apr 2015 14:21:49 -0400
From:	Steven Rostedt <rostedt@...dmis.org>
To:	Ingo Molnar <mingo@...nel.org>
Cc:	"Paul E. McKenney" <paulmck@...ux.vnet.ibm.com>,
	Clark Williams <williams@...hat.com>,
	linux-kernel@...r.kernel.org, torvalds@...ux-foundation.org,
	a.p.zijlstra@...llo.nl, akpm@...ux-foundation.org,
	linux-rt-users@...r.kernel.org
Subject: Re: [GIT RFC PULL rcu/urgent] Prevent Kconfig from asking pointless
 questions

On Mon, 20 Apr 2015 20:09:04 +0200
Ingo Molnar <mingo@...nel.org> wrote:


> So the disadvantage is that if a boot default is wrong, we'll hear 
> about it eventually and can fix/improve it.
> 
> If a sysctl knob is wrong, people will just 'tune' it and forget to 
> propagate it to the kernel proper (why should they).

My fear is that there is no one true value. One person complains about
it, we change it, then someone else complains about the new value. That
would be even worse.

> 
> Which is fine for something like ftrace and other ad-hoc 
> instrumentation that is generally very fine tuned to a given bug or 
> given piece of hardware, but for something like the RCU implementation 
> of the kernel - even if it's just a RT side thought of it - I'm not so 
> sure about it.

I would argue than every case is different, and only the sysadmin would
know the right value. Thus, just set it to one, and if that's not good
enough, then the sysadmins can change it to their needs.

-- Steve
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