How to configure flushing klog by syslog

[Peter Skvarka <ps%softinengines.com@localhost>]

Hello,
I am trying to use printf() in kernel module for debugging purposes and 
I cannot find how to force flushing klog by syslogd.
I found syslogd option -S. Manual page says: "
-S               Sync kernel messages to disk immediately.

After adding to rc.conf: syslogd_flags="-S" nothing changes.
Does exist way how to flush message from kernel c code (something 
similar like flush(FILE*) in user mode) or by any change in kernel 
settings or services configuration ?

Peter