printk kernel logging for router

printk kernel logging for router

[william fitzgerald]

hi all,
linux newbie here.

i need to know some information in regard to
logging with printk statements.

my plan is to monitor the performance of a linux
router.i'm adding printk  statements to the
kernel to every function that is called by
forwarding packets and in that way find precisely
where a packet or packets  get lost.

 this is still in progress.

when i finally get all my printk statements in, i
want to be able to flood my router on my own mini
network.(router running on a p133 using
redhat7.1)

my understanding of printk is that each time it
is encountered it is written to disk.so for a lot
of packets there will be alot of writes,
therefore slowing the system and producing false
results.

so how to i buffer or record  the printk
statements and print them to disk  after my
packets have gone through the router?

 do i edit the printk.c file and change the 
line:

                          static char buf[1024];

and increase the size of the array?
or do i edit the klogd.c program and change
something in there?

 many thanks in advance and all comments no
matter how trivial  are welcome in  order for me
to learn more.

regards william.

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Re: printk kernel logging for router

[Erik Mouw]

On Fri, Nov 09, 2001 at 03:41:17PM +2400, william fitzgerald wrote:
> hi all,
> linux newbie here.

You might be interested in the kernelnewbies.org website, mailinglist,
and IRC channel.

> i need to know some information in regard to
> logging with printk statements.
> 
> my plan is to monitor the performance of a linux
> router.i'm adding printk  statements to the
> kernel to every function that is called by
> forwarding packets and in that way find precisely
> where a packet or packets  get lost.
> 
>  this is still in progress.

Don't be surprised if all that printing will degrade the performance of
your router.

> when i finally get all my printk statements in, i
> want to be able to flood my router on my own mini
> network.(router running on a p133 using
> redhat7.1)
> 
> my understanding of printk is that each time it
> is encountered it is written to disk.so for a lot
> of packets there will be alot of writes,
> therefore slowing the system and producing false
> results.

Printk doesn't write to disk, syslogd does.

> so how to i buffer or record  the printk
> statements and print them to disk  after my
> packets have gone through the router?
> 
>  do i edit the printk.c file and change the 
> line:
> 
>                           static char buf[1024];
> 
> and increase the size of the array?
> or do i edit the klogd.c program and change
> something in there?

Change /etc/syslogd.conf. Put all kernel messages into a separate
logging file and put a '-' before the log file name so syslogd will not 
sync the file after each write. See man syslogd, klogd, syslog.conf


Erik

-- 
J.A.K. (Erik) Mouw, Information and Communication Theory Group, Faculty
of Information Technology and Systems, Delft University of Technology,
PO BOX 5031, 2600 GA Delft, The Netherlands  Phone: +31-15-2783635
Fax: +31-15-2781843  Email: J.A.K.Mouw@its.tudelft.nl
WWW: http://www-ict.its.tudelft.nl/~erik/