linux-kernel - Re: [PATCH 1/7] x86: Limit the number of processor bootup messages

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Message-ID: <86802c440911121410v30c5b00ewdd9ada71096b4e65@mail.gmail.com>
Date:	Thu, 12 Nov 2009 14:10:35 -0800
From:	Yinghai Lu <yhlu.kernel@...il.com>
To:	Mike Travis <travis@....com>
Cc:	Ingo Molnar <mingo@...e.hu>, 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>,
	Andi Kleen <andi@...stfloor.org>,
	Greg Kroah-Hartman <gregkh@...e.de>,
	"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@...r.kernel.org
Subject: Re: [PATCH 1/7] x86: Limit the number of processor bootup messages

On Thu, Nov 12, 2009 at 9:19 AM, Mike Travis <travis@....com> wrote:
> With a large number of processors in a system there is an excessive amount
> of messages sent to the system console.  It's estimated that with 4096
> processors in a system, and the console baudrate set to 56K, the startup
> messages will take about 84 minutes to clear the serial port.
>
> 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.
>
> The list of message transformations....
>
> For system_state == SYSTEM_BOOTING:
>
> [   18.669304] Booting Node   0, Processors  1 2 3 4 5 6 7 Ok.
> [   19.321065] Booting Node   1, Processors  8 9 10 11 12 13 14 15 Ok.
> [   20.065325] Booting Node   2, Processors  16 17 18 19 20 21 22 23 Ok.
> ..
> [  117.153053] Booting Node  63, Processors  1016 1017 1018 1019 1020 1021 1022 1023 Ok.
> [  117.952235] Brought up 1024 CPUs
>
> Timing shows that with NO bootup messages, it takes only slightly less time
> so printing adds very little overhead:
>
> [   18.670219] Booting all processors
> [  117.180248] Brought up 1024 CPUs
>
> For Processor Information printout, the specifics of CPU0 are printed and
> then at the end of the bootup sequence, a summary is printed:
>
> [  117.957682] Processor Information for CPUS: 0-191,208-223,256-271,...
> [  117.968034] Genuine Intel(R) CPU             0000 @ 2.13GHz stepping 04
> [  117.977406] BogoMIPS: MIN 3989.01 (7978031) AVG 4266.62 (8533249) MAX 4537.51 (9075028)
> [  117.984496] Processor Information for CPUS: 192-207,240-255,272-287,...
> [  117.996032] Genuine Intel(R) CPU             0000 @ 2.13GHz stepping 03
> [  118.001404] BogoMIPS: MIN 4021.49 (8042995) AVG 4265.91 (8531833) MAX 4479.79 (8959584)
> [  118.012373] Processor Information for CPUS: 224-239,736-751
> [  118.020032] Genuine Intel(R) CPU             0000 @ 1.87GHz stepping 03
> [  118.028033] BogoMIPS: MIN 3733.92 (7467855) AVG 3746.96 (7493933) MAX 3939.52 (7879056)
> [  118.036360] Processor Information for CPUS: 320-335,384-415,432-447,...
> [  118.044032] Intel(R) Xeon(R) CPU           X7560  @ 2.27GHz stepping 05
> [  118.053404] BogoMIPS: MIN 4244.65 (8489318) AVG 4532.45 (9064917) MAX 4666.80 (9333604)
> [  118.060644] Total of 1024 processors activated (4386353.46 BogoMIPS).
>
>
> The following lines have been removed:
>
>        CPU: Physical Processor ID:
>        CPU: Processor Core ID:
>        CPU %d/0x%x -> Node %d

why?
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