short explanation -jiffies (newbie)

Hello,
can someone give a short explanation what jiffies are? regards
sting

_________________________________________________________________
Add photos to your e-mail with MSN 8. Get 2 months FREE*. http://join.msn.com/?page=features/featuredemail

It is a variable that keeps increasing forever until it wraps back to zero at which time it still keeps increasing. It gets increased at the HZ (a defined constant) rate as a result of a hardware interrupt.

It is used for various timing functions within the kernel.

Cheers,
Dick Johnson
Penguin : Linux version 2.4.22 on an i686 machine (797.90 BogoMips).
Note 96.31% of all statistics are fiction.

A short explanation :

"Basic packet of kernel time, around 10ms on x86. Related to HZ, the basic resolution of the operating system. The timer interrupt is raised each 10ms, which then performs some h/w timer related stuff, and marks a couple of bh's ready to run if applicable."

is given at :

http://www.kernelnewbies.org/glossary/#J

For more details you could take a look at these files (there are more) in the kernel source :

include/linux/delay.h
init/main.c

to find more relevant files try something like this in the kernel source tree :

for i in find -name *.[ch]; do grep -H jiffy $i; done

Kind regards,

Jesper Juhl