Re: nohz: Warn if the machine can not perform nohz_full
From: Frederic Weisbecker
Date: Mon Jul 15 2013 - 21:10:51 EST
On Mon, Jul 15, 2013 at 03:30:20PM -0400, Steven Rostedt wrote:
> 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 ***
> ***************************************************************
> ***************************************************************
> ***************************************************************
> ***************************************************************
May be we can try that. In fact I have a pending patch that converts the
stacktrace warning to a one line printk message, as Ingo reported that issue
to me. But the risk is that it can be indeed lost in the flow.
>
>
> 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.
Well the above example is unlikely to be missed. If it is, then I believe a
traditional warning would be lost as well.
>
> -- Steve
>
>
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