linux-kernel - Re: [PATCH] Prevent users from disabling tickless

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Date:	Wed, 22 Dec 2010 14:32:29 -0800
From:	Frank Rowand <frank.rowand@...il.com>
To:	Matthew Wilcox <matthew@....cx>
Cc:	Frank Rowand <frank.rowand@...sony.com>,
	Thomas Gleixner <tglx@...utronix.de>,
	Arjan van de Ven <arjan@...radead.org>,
	linux-kernel@...r.kernel.org
Subject: Re: [PATCH] Prevent users from disabling tickless

On Wed, Dec 22, 2010 at 1:34 PM, Matthew Wilcox <matthew@....cx> wrote:
>
> On Wed, Dec 22, 2010 at 01:00:37PM -0800, Frank Rowand wrote:
> > Why remove the ability to make the configuration choice?  Why not
> > just add the info about performance impact to the help text and
> > let me shoot myself in the foot (that is the unix way (tm)) if
> > I desire to?
>
> $ wc -l .config
> 2601 .config
>
> It's too hard to get every single config option right ... unless it's a
> works / doesn't work choice, having a "make my performance suck" config
> option is a bad idea.

(And yet one more duplicate, because lkml rejected my previous reply. Sorry!!)
(sorry for the duplicate, I dropped the cc's on my previous reply)

Agreed that setting config options can be painful!

Various options that improve performance for your system  can negatively impact
the performance of systems and applications that are different than your system.
On some of my real time systems, CONFIG_NO_HZ=y results in larger maximum
interrupts disabled values, meaning larger real time latency.

For the option in question, would it be sufficient to just add
"default y", so that the
common case gets the correct value, but the value remains configurable?

-Frank
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