Re: Can and should the kernel HZ value be changed?

Sitaram Iyer (ssiyer@cs.rice.edu)
Sun, 3 Jan 1999 15:11:23 -0600


Thus, Albert D. Cahalan wrote...
> > The default value of HZ is 100hz. Since the DEF_PRIORITY in sched.h
> You can and should change HZ, but might cause trouble. If you set
> the value to 1024 (like the Alpha uses) your clock rolls over in
> about 50 days. Maybe you reboot every month and do not care.

I presume decreasing HZ might be good for improving the throughput on
computational jobs, compilation etc. and would kill interactivity, so
what if the scheduler monitors the type of processes running (whether
they exhaust their timeslices, for eg.) and decides on a nice value of
HZ every 10 seconds or so (maybe choose between the permissible values),
with HZ #defined to get_HZ().. wondering how intimately the rest of the
code depends on HZ being a constant, and whether the constant-HZ
dependent parts can't be kicked into reading the new value.. hmm?

Sitaram

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