linux-kernel - Re: [PATCH] hrtimer: Remove overly verbose "switch to high res mode" message

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Date:	Thu, 24 Sep 2009 22:42:09 -0400
From:	Valdis.Kletnieks@...edu
To:	Roland Dreier <rdreier@...co.com>
Cc:	Joe Perches <joe@...ches.com>, Ingo Molnar <mingo@...e.hu>,
	Thomas Gleixner <tglx@...utronix.de>,
	linux-kernel@...r.kernel.org
Subject: Re: [PATCH] hrtimer: Remove overly verbose "switch to high res mode" message

On Thu, 24 Sep 2009 14:15:14 PDT, Roland Dreier said:
> 
>  > > -	printk(KERN_DEBUG "Switched to high resolution mode on CPU %d\n",
>  > > -	       smp_processor_id());
>  > 
>  > Perhaps pr_debug instead?
>  > It gets compiled to nothing unless DEBUG is defined.
> 
> Dunno... is that kernel log message ever useful now?

There's 3 cases to consider:

1) Kernel built with CONFIG_HIGH_RES_TIMERS=n.  We get no message then.

2) We have high-res timers and it succeeded. We probably don't care if that's
the usual case, so lose the message in that case, just like we probably
don't need a message that we managed to fork off init.

3) We attempted to switch to high-res mode, and it *failed*. We already throw
the appropriate KERN_WARNING for that a few lines up.

And since we issue a message in the one case we *care* about, we can
determine that the *lack* of that KERN_WARNING means the switch went OK.

Thus, we don't need the message, as it doesn't *tell* us anything we didn't
already know.

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