linux-kernel - Re: [PATCH] x86_64: Limit the number of processor bootup messages

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Message-ID: <20091102193445.GA9948@elte.hu>
Date:	Mon, 2 Nov 2009 20:34:45 +0100
From:	Ingo Molnar <mingo@...e.hu>
To:	Mike Travis <travis@....com>
Cc:	Andi Kleen <ak@...ux.intel.com>,
	Thomas Gleixner <tglx@...utronix.de>,
	Andrew Morton <akpm@...ux-foundation.org>,
	Heiko Carstens <heiko.carstens@...ibm.com>,
	Roland Dreier <rdreier@...co.com>,
	Randy Dunlap <rdunlap@...otime.net>, Tejun Heo <tj@...nel.org>,
	Greg Kroah-Hartman <gregkh@...e.de>,
	Yinghai Lu <yinghai@...nel.org>,
	"H. Peter Anvin" <hpa@...or.com>,
	David Rientjes <rientjes@...gle.com>,
	Steven Rostedt <rostedt@...dmis.org>,
	Rusty Russell <rusty@...tcorp.com.au>,
	Hidetoshi Seto <seto.hidetoshi@...fujitsu.com>,
	Jack Steiner <steiner@....com>,
	Frederic Weisbecker <fweisbec@...il.com>, x86@...nel.org,
	Linux Kernel <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH] x86_64: Limit the number of processor bootup messages


* Mike Travis <travis@....com> wrote:

>
>
> Andi Kleen wrote:
>> Mike Travis wrote:
>>>
>>> This set of patches limits the number of repetitious messages which  
>>> contain
>>> no additional information.  Much of this information is obtainable  
>>> from the
>>> /proc and /sysfs.   Most of the messages are also sent to the kernel log
>>> buffer as KERN_DEBUG messages so it can be used to examine more  
>>> closely any
>>> details specific to a processor.
>>
>> What would be good is to put the information from the booting CPUs
>> into some buffer and print it visibly if there's a timeout detected on  
>> the BP.
>
> What do you think of this idea....  Add a "mark kernel log buffer" 
> function, and then if any KERN_NOTE or above happens, it sends the 
> marked info from the kernel log buffer to the console before the 
> current message.  Set the marker to '0' to clear.

That's _way_ too complex really, for little benefit. (If there's a boot 
hang people will re-try anyway (and this time with a serial console 
attached or so), and they can add various boot options to increase 
verbosity - depending in which phase the bootup hung.)

So please go with the simple solution i suggested days ago: print stuff 
on the boot CPU but after that only a single line per AP CPU.

	Ingo
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