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: [phone]
Fax: [phone]  Email: [e-mail]
WWW: http://www-ict.its.tudelft.nl/~erik/