linux-kernel - Re: nohz: Warn if the machine can not perform nohz

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Message-ID: <1373916620.17876.182.camel@gandalf.local.home>
Date:	Mon, 15 Jul 2013 15:30:20 -0400
From:	Steven Rostedt <rostedt@...dmis.org>
To:	Dave Jones <davej@...hat.com>
Cc:	Frederic Weisbecker <fweisbec@...il.com>,
	Linux Kernel Mailing List <linux-kernel@...r.kernel.org>
Subject: Re: nohz: Warn if the machine can not perform nohz_full

On Mon, 2013-07-15 at 14:56 -0400, Dave Jones wrote:
> On Mon, Jul 15, 2013 at 02:49:42PM -0400, Steven Rostedt wrote:
>  
> Is a printk not enough for that purpose ? Tainting the kernel is kinda anti-social.
> 

printk's don't usually get peoples attention. Taints and warnings do. If
the hardware doesn't allow for nohz-full, and the only way to enable it
is via kernel command line, how do you scream to the user that it isn't
going to work.

We could do a large banner saying:

***************************************************************
***************************************************************
***************************************************************
***************************************************************
***                    UNSTABLE TSC                         ***
***                NO_HZ_FULL disabled                      ***
***************************************************************
***************************************************************
***************************************************************
***************************************************************


And not do the warning. Maybe that will get peoples attentions?

But then again, this could be lost in the boot up if the box prints a
lot of data.

-- Steve


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