Re: HZ, preferably as small as possible

Jeff Garzik
2002-07-11T02:58:41Z

Grover, Andrew wrote:
> So, a changing tick *can* be done. If Linux does the same thing, seems like
> everyone is happy. What are the obstacles to this for Linux? If code is
> based on the assumption of a constant timer tick, I humbly assert that the
> code is broken.

Unfortunately code in Linux has traditionally compiled in a constant HZ
all over the place, and jiffies instead of real time units are at the
heart of all Linux timer-related activities.

I don't see that making 'HZ' a variable is really an option, because
many drivers and scheduler-related code will be wildly inaccurate as
soon as HZ actually changes values.

So that leaves us with the option of changing all the code related to
waiting to be based on msecs and usecs. Which I would love to do, but
that's a lot of work, both code- and audit-wise.

Jeff