RTAI LiveCD + DB update

Panagiotis Issaris panagiotis.issaris at mech.kuleuven.ac.be
Sat Oct 16 16:19:03 CEST 2004


Hi,

Philippe Gerum wrote:

>The problem might be that spurious LXRT load induced by such sleeping
>state might keep increasing over time, at least to the point where they
>become significant wrt hackbench figures. In fact, any LXRT task running
>in hard mode also sleeps in TASK_UNINTERRUPTIBLE mode after it has been
>stolen away from the Linux scheduler; this impacts the Linux loadavg the
>same way, but in this case, this could be construed as a real load since
>the RT side actually runs here. So we have two opposite situations
>charged for the same result.
>
>I did not specifically investigate the matter, but I suspect that such
>results would carry too much uncertainty for proper interpretation.
>  
>
Thanks for the explanation!
Then I shall remove them from the LiveCD and DB.

>>Or should I better remove that data from the DB? Or can
>>I use some other metric for calculating load (which is valid
>>when running RTAI/LXRT)?
>>
>>    
>>
>
>Using the execution time figures available from /proc/rtai/ scheduler
>might be a better information than Linux's loadavg for LXRT, even if
>they don't refer to the same kind of load.
>  
>
I will add those.

>>What data should best be added from the other tests (preempt,switch)?
>>    
>>
>
>Interesting data that immediately come to my mind are:
>o interrupt propagation time in the Adeos layer (Adeos needs to provide
>the info here -- I'm going to add that in the next release);
>  
>
I'll add them as soon as they are available.

>o for x86, average programming time of the 8254, especially under
>saturated bus conditions (e.g. dd if=/dev/zero of=<hdd-file> count=X
>bs=1M); this directly impacts the quality of the scheduling latency
>calibration in one-shot mode;
>  
>
Does dd if=/dev/hdc of=/dev/null count=X bs=1M give a
similar effect with respect to bus saturation?

With friendly regards,
Takis

-- 
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Panagiotis Issaris
Katholieke Universiteit Leuven
Division Production Engineering,
Machine Design and Automation
Celestijnenlaan 300B              panagiotis.issaris at mech.kuleuven.ac.be
B-3001 Leuven Belgium                 http://www.mech.kuleuven.ac.be/pma
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