From mboxrd@z Thu Jan  1 00:00:00 1970
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Date: Fri, 11 Aug 2006 10:14:58 +0200
From: Wolfgang Grandegger <wg@domain.hid>
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Subject: Re: [Xenomai-help] PPC posted results (testsuite latency)
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To: GUARDIOLA-FALCO Sebastien 204282 <Sebastien.GUARDIOLA-FALCO@domain.hid>
Cc: xenomai@xenomai.org, jan.kiszka@domain.hid

GUARDIOLA-FALCO Sebastien 204282 wrote:
> jan.kiszka wrote:
>> == Sampling period: 100 us
>>  == All results in microseconds
>> RTT|  00:00:01
>> RTH|-----lat min|-----lat avg|-----lat max|-overrun|----lat best|---lat worst
>> RTD|       1.859|       3.239|       6.179|       0|       1.859|       6.179
>> RTD|       2.159|       3.239|      13.559|       0|       1.859|      13.559
>> ...
> 
>> Looks quite good, maybe too good. Did you load your box? See
>> TROUBLESHOOTING for some hints on this. Also let it run for a longer period.
> 
> What do you mean by "too good"? What could be a cause of these results?
> 
> I've tested on a 5-10 minutes basis.
> For calculations loads, I tested Linux ones (like http://www.tux.org/~mayer/linux/bmark.html) that take 99% of CPU usage.
> Then I used the same one compiled for Xenomai. Latency results were almost the same.
> Only Linux commands seems to disturb Xenomai. I tested some "ps" and "top", locally and from a telnet connection.
> Results : I reach to 4.x avg latency, and 50 worse.

The interesting figure is the worst case latency under load. If I 
understood you correctly, you measured 50 + 4.5 us worse case. This is a 
more resonable number for you system. Nevertheless, the big L2 cache 
should help.

> Any other idea? May be a huge NFS file transfer, or socket transfer, I don't know.

I normally do "while ls; do ls; done" on the console and "ping -f 
<server-ip>" in another telnet window. It's typical that the latency 
jumps when you do a telnet, etc.

Wolfgang.