Re: [PATCH] x86_64: Limit the number of processor bootup messages
From: Mike Travis
Date: Mon Nov 02 2009 - 15:32:19 EST
Ingo Molnar wrote:
* Mike Travis <travis@xxxxxxx> wrote:
Andi Kleen wrote:
Mike Travis wrote:
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.
This set of patches limits the number of repetitious messages which
containWhat would be good is to put the information from the booting CPUs
no additional information. Much of this information is obtainable
/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
details specific to a processor.
into some buffer and print it visibly if there's a timeout detected on
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.)
I'm ok with this, though generally speaking large server systems have
serial consoles attached, and save the output into admin logs. One
problem with just setting the loglevel high enough to output debug
messages, is you get literally 100's of thousands of lines of meaningless
information. We waited over 8 hours for a system with 2k cpus to boot
in debug mode, and it never made it all the way up.
My intention for the above was to attempt to print debug information
that pertains to the failure, and not everything else.
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.
So you think printing 4096 lines provides meaningful additional
information? I would think at least compress it so you only print
each new processor socket boots and not the 16 threads each of
I should have timing information soon for 512 cores/1024 threads and
printing a single line for each of those will significantly increase
the time it takes to boot.
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