Reduce boot time console messages?

Reduce boot time console messages?

[Woody Wu]

Hi,

My kernel is printing too many messages at boot time from a special
device driver (j2ffs filesystem). I belive these kernel messages are
level DEBUG. If don't change the kernel code, is there anyway to print
only some higher level of messages?

Thanks in advance.

-- 
I can't go back to yesterday - because I was a different person then

Reduce boot time console messages?

[Valdis.Kletnieks at vt.edu]

On Sat, 03 Aug 2013 20:27:55 +0800, Woody Wu said:
> Hi,
>
> My kernel is printing too many messages at boot time from a special
> device driver (j2ffs filesystem). I belive these kernel messages are
> level DEBUG. If don't change the kernel code, is there anyway to print
> only some higher level of messages?

In your kernel source tree, there's a file called Documentation/kernel-parameters.txt
and in it, we find documentation  of the following two boot-time parameters:


        ignore_loglevel [KNL]
                        Ignore loglevel setting - this will print /all/
                        kernel messages to the console. Useful for debugging.
                        We also add it as printk module parameter, so users
                        could change it dynamically, usually by
                        /sys/module/printk/parameters/ignore_loglevel.
...

        loglevel=       All Kernel Messages with a loglevel smaller than the
                        console loglevel will be printed to the console. It can
                        also be changed with klogd or other programs. The
                        loglevels are defined as follows:

                        0 (KERN_EMERG)          system is unusable
                        1 (KERN_ALERT)          action must be taken immediately
                        2 (KERN_CRIT)           critical conditions
                        3 (KERN_ERR)            error conditions
                        4 (KERN_WARNING)        warning conditions
                        5 (KERN_NOTICE)         normal but significant condition
                        6 (KERN_INFO)           informational
                        7 (KERN_DEBUG)          debug-level messages

In addition, there may or may not be a module parameter to control the
logging level of the particular module - look for the word 'debug' in that
file.  There's also the 'dynamic debugging' facility which the module may
be coded to support....
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Reduce boot time console messages?

[Woody Wu]

On Sat, Aug 03, 2013 at 10:08:42AM -0400, Valdis.Kletnieks at vt.edu wrote:
> On Sat, 03 Aug 2013 20:27:55 +0800, Woody Wu said:
> > Hi,
> >
> > My kernel is printing too many messages at boot time from a special
> > device driver (j2ffs filesystem). I belive these kernel messages are
> > level DEBUG. If don't change the kernel code, is there anyway to print
> > only some higher level of messages?
> 
> In your kernel source tree, there's a file called Documentation/kernel-parameters.txt
> and in it, we find documentation  of the following two boot-time parameters:
> 
> 
>         ignore_loglevel [KNL]
>                         Ignore loglevel setting - this will print /all/
>                         kernel messages to the console. Useful for debugging.
>                         We also add it as printk module parameter, so users
>                         could change it dynamically, usually by
>                         /sys/module/printk/parameters/ignore_loglevel.
> ...
> 
>         loglevel=       All Kernel Messages with a loglevel smaller than the
>                         console loglevel will be printed to the console. It can
>                         also be changed with klogd or other programs. The
>                         loglevels are defined as follows:
> 
>                         0 (KERN_EMERG)          system is unusable
>                         1 (KERN_ALERT)          action must be taken immediately
>                         2 (KERN_CRIT)           critical conditions
>                         3 (KERN_ERR)            error conditions
>                         4 (KERN_WARNING)        warning conditions
>                         5 (KERN_NOTICE)         normal but significant condition
>                         6 (KERN_INFO)           informational
>                         7 (KERN_DEBUG)          debug-level messages

Valdis, thank you very much.  I just passed loglevel=7 as kernel command
line and hope it can suspress KERN_DEBUG messages printed out to console
at boot time. But, it seems not work. A lot of debug level messages from
jffs2 module still print out. I will go to check where is wrong.

> 
> In addition, there may or may not be a module parameter to control the
> logging level of the particular module - look for the word 'debug' in that
> file.  There's also the 'dynamic debugging' facility which the module may
> be coded to support....



-- 
I can't go back to yesterday - because I was a different person then

Reduce boot time console messages?

[Valdis.Kletnieks at vt.edu]

On Mon, 05 Aug 2013 11:07:26 +0800, Woody Wu said:

> Valdis, thank you very much.  I just passed loglevel=7 as kernel command
> line and hope it can suspress KERN_DEBUG messages printed out to console
> at boot time. But, it seems not work. A lot of debug level messages from
> jffs2 module still print out. I will go to check where is wrong.

Weird.  Do the "debugging" messages actually have the string '[JFFS2 DBG]'
in them?  If not, then they're some *other* messages from jffs2.

Also, double-check you don't have ignore_loglevel in the kernel command line.
(This one can be tricky - do a 'cat /proc/cmdline' once you're booted to see
what you really had - there's support for compiling in all/part of a commandline
to work around buggy boot loaders that only support insanely short parameter
lists - so what your  boot loader said it passed to the kernel may not be
what the kernel used).
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Reduce boot time console messages?

[Woody Wu]

On Mon, Aug 05, 2013 at 12:44:49AM -0400, Valdis.Kletnieks at vt.edu wrote:
> On Mon, 05 Aug 2013 11:07:26 +0800, Woody Wu said:
> 
> > Valdis, thank you very much.  I just passed loglevel=7 as kernel command
> > line and hope it can suspress KERN_DEBUG messages printed out to console
> > at boot time. But, it seems not work. A lot of debug level messages from
> > jffs2 module still print out. I will go to check where is wrong.
> 
> Weird.  Do the "debugging" messages actually have the string '[JFFS2 DBG]'
> in them?  If not, then they're some *other* messages from jffs2.
> 
> Also, double-check you don't have ignore_loglevel in the kernel command line.
> (This one can be tricky - do a 'cat /proc/cmdline' once you're booted to see
> what you really had - there's support for compiling in all/part of a commandline
> to work around buggy boot loaders that only support insanely short parameter
> lists - so what your  boot loader said it passed to the kernel may not be
> what the kernel used).

Sorry for such late reply.  Those dirty messages from jffs2 doesn't have
'[JFFS2 DBG]' or other prefixes.  Okay, I will look up the kernel source
again, to see if there are really KERN_DEBUG level. 

Btw: How can I know what command line parameters a module can
recogonize? I remember there is a definition to search in kernel .c
files.

Thanks.

-- 
I can't go back to yesterday - because I was a different person then