Re: can we measure the traffic between user and kernel mode

Here the libc has grouped all your printfs into one single system call because of user-space buffering. Fortunately you can prevent this behavior using unbuffer:

http://linuxcommand.org/man_pages/unbuffer1.html

Sorry, that should have read stdbuf, and the correct man page is here: http://www.pixelbeat.org/programming/stdio_buffering/stdbuf-man.html Alex.