Messages in this thread | | | Date | Tue, 29 Mar 2005 18:24:16 -0600 | From | Chris Friesen <> | Subject | Re: How to measure time accurately. |
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Peter Chubb wrote: >>>>>>"Chris" == Chris Friesen <cfriesen@nortel.com> writes:
> Chris> Most cpus have some way of getting at a counter or decrementer > Chris> of various frequencies. Usually it requires low-level hardware > Chris> knowledge and often it needs assembly code. > > As a device driver is inside the linux kernel (unless you're writein a > user-mode device driver :-)) you can use the getcycles() macro that's > defined for most architectures. It provides a snapshot of the > cycle-counter.
For ppc this only gives 32-bit values, which overflow every 129 seconds on my G5. Depending on how long you're trying to time, this could be a problem.
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