short explanation -jiffies (newbie)

short explanation -jiffies (newbie)

[sting sting]

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

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Re: short explanation -jiffies (newbie)

[Richard B. Johnson]

On Thu, 16 Oct 2003, sting sting wrote:

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

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.

Re: short explanation -jiffies (newbie)

[Jesper Juhl]

On Thu, 16 Oct 2003, sting sting wrote:

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

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