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From Thor Heinrichs-Wolpert <t...@lunartek.com>
Subject Re: Profiling Pipeline [was Re: [RT] Unit testing and CocoonUnit]
Date Tue, 04 Nov 2003 19:23:11 GMT
If you try to profile on a Unix environment based on timings you have 
to do multiple passes and get a statistical average to be meaningful.  
The timer functionality in the kernel or user space is at such a low 
priority that effectively it jumps between values ... that's why when 
tuning using tools like sar you have to set a decent sample size.  This 
is pretty much the case for any current non-realtime OS.  For long 
running tasks the time is probably OK, for small times ( < 10 ms  or 
even .1s timings ) on a busy system the times are just erroneous.

Cheers,
Thor HW

On 3-Nov-03, at 9:36 AM, Nicola Ken Barozzi wrote:

> Berin Loritsch wrote:
> ...
>> I have a feeling the timings are useless largely because of the 
>> granularity
>> of the System.getTimeInMillis() method.  On Windows the granularity 
>> is 10 ms.
>> If the timing is less than that it registers as 0.  Add enough zeros 
>> and it
>> will always be less than the total time for the timing.
>
> There is a way of getting around this by using JNI and calling the 
> correct stuff. If you Google round you will sure find something. 
> Probably there is something at www.javaworld.com.
>
> -- 
> Nicola Ken Barozzi                   nicolaken@apache.org
>             - verba volant, scripta manent -
>    (discussions get forgotten, just code remains)
> ---------------------------------------------------------------------
>
>
>


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