TOP shows above 100% WCPU usage

Chuck Swiger cswiger at mac.com
Thu Aug 17 16:48:45 UTC 2006


On Aug 16, 2006, at 10:28 PM, Bill LeFebvre wrote:
>>> You have multiple CPUs, so a threaded process can theoretically  
>>> reach
>>> 100*ncpus cpu usage.
>>>
>> Ahh, thats makes sense, thanks.
>
> Actually it doesn't.  IMO, %CPU should be biased for all available  
> cpu, not just a single cpu.  In other words, a single-threaded  
> process running on a two processor box should never see more than  
> 50% cpu.  That's how top computes it for SunOS.  But for freebsd  
> top only displays whats in the proc structure and I don't know off- 
> hand how the kernel records it.

You've got a good point here.  In particular, consider the case where  
you have an SMP machine where not all of the CPUs are running at the  
same clock rate...100% of one CPU is not the same level of processing  
as 100% of another.

-- 
-Chuck



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