On Fri, 2009-02-13 at 17:00 +0000, [email protected] wrote:
>
> As far as I know the timer interrut rate in RHEL 4 is 100 and
> in RHEL 5 it is 1000. The command "getconf CLK_TCK" are supposed to
> return
> the timer interrupt rate, but seems to return 100 regardless of the
> actual rate. Do you know any reliable way to find the timer interrupt
> rate?
>
I don't think so. I think HZ is defined as 1000 in RHEL4 and RHEL5.
4.7 and 5.1(?) added a feature - clock-tick-divider which allows you set a
divider.
4.7 release notes:
The divider=[value] option is a kernel command-line parameter that
allows you to adjust the system clock rate while maintaining the same
visible HZ timing value to user space applications.
Using the divider=[value] option allows you to reduce CPU
overhead and increase efficiency at the cost of lowering the
accuracy of timing operations and profiling. This is useful in
virtualized environments as well as for certain applications.
Useful [values] for the standard 1000Hz clock are:
* 2 = 500Hz
* 4 = 250Hz
* 10 = 100Hz (value used by previous releases of Red Hat
Enterprise Linux)
Note that the virtualized kernel uses a 250HZ clock by default.
As such, it does not need the divider=[value] option either in
dom0 or in paravirtualized guests.
Without source examination, a little experimentation with
/proc/interrupts will get you the answer. Cat it out, wait 60 sec,
and cat it again. Diff the timer and you'll be close.
Kbase article
http://kbase.redhat.com/faq/docs/DOC-3115
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