On 24/01/08 11:02, Gilles Chanteperdrix wrote:
> On Jan 24, 2008 10:41 AM, Juan Antonio Garcia Redondo
> <[EMAIL PROTECTED]> wrote:
> >
> > On 23/01/08 14:15, Gilles Chanteperdrix wrote:
> > > On Jan 23, 2008 11:04 AM, Gilles Chanteperdrix
> > > <[EMAIL PROTECTED]> wrote:
> > > > On Jan 23, 2008 7:52 AM, Juan Antonio Garcia Redondo
> > > >
> > > > <[EMAIL PROTECTED]> wrote:
> > > > > I see everything OK except for the first samples of cyclictests. Any
> > > > > comments ?
> > > >
> > > > The load you apply does not load the cache, which is a source of
> > > > jitter. You should run the cache calibrator (I do not find the cache
> > > > calibrator URL, but it is somewhere in Xenomai distribution or wiki).
> > >
> > > It is in the TROUBLESHOOTING guide, question "How do I adequately stress
> > > test".
> > >
> > > --
> > > Gilles Chanteperdrix
> >
> > Thanks Gilles, I've done more tests using the cache calibrator from
> > http://www.cwi.nl/~manegold/Calibrator. The latency numbers are very
> > similar althought I've found an strange behaviour related to telnet
> > sessions.
>
> Are you kidding ? In the first results you posted, the latency was
> around 80us whereas now, you get a latency around 130us. And from I
> read, you did not run the tests for long period. If you want reliable
> results, you should let the test run, under load, for hours.
Well, after several tests, (one of them 4 hours long), I can't see
latencies above 100 us. Anyway I'll do more tests this weekend. The
latency around 130us occurs with telnet activity.
>
> >
> > Environment:
> > o Tests running from console over atmel serial port.
> > o A telnet session over on-chip ethernet.
> > o System without load.
> >
> > ./latency -p 500 -t0
> > == All results in microseconds
> > warming up...
> > RTT| 00:00:01 (periodic user-mode task, 500 us period, priority 99)
> > RTH|-RTH----lat min|-----lat avg|-----lat max|-overrun|----lat best|---lat
> > worst
> > RTD| 49.613| 52.190| 62.822| 0| 49.613| 62.822
> > RTD| 42.203| 52.512| 66.365| 0| 42.203| 66.365
> >
> >
> > Now If hit a key on the telnet session :
> >
> > RTD| 36.726| 57.989| 109.536| 0| 31.572| 109.536
> > <-------- Here I've hit the key.
> > RTD| 36.404| 51.868| 69.587| 0| 31.572| 109.536
> > RTD| 35.760| 51.868| 73.775| 0| 31.572| 109.536
> >
> > Now, I launch an script which executes four instances of cache
> > calibrator.
> >
> > RTD| 45.103| 57.667| 75.708| 0| 32.538| 122.422
> > RTD| 45.425| 57.023| 76.030| 0| 32.538| 122.422
> > RTD| 46.069| 57.023| 75.708| 0| 32.538| 122.422
> >
> > Now, I can hit a key on the telnet session without effects over latency
> > numbers:
> >
> > RTD| 44.136| 57.989| 75.386| 0| 27.384| 128.221
> > RTD| 46.713| 57.345| 76.353| 0| 27.384| 128.221
> > RTD| 44.780| 57.345| 76.675| 0| 27.384| 128.221
> > RTD| 43.492| 56.701| 76.997| 0| 27.384| 128.221
> >
> > Now I stop the calibrator process and launch 'ping -f -s2048 192.168.2.82'
> > from an external
> > machine.
> >
> > RTD| 40.270| 68.621| 90.850| 0| 27.384| 128.221
> > RTD| 36.082| 68.621| 88.273| 0| 27.384| 128.221
> > RTD| 40.592| 67.976| 91.494| 0| 27.384| 128.221
> > RTD| 41.237| 68.298| 89.239| 0| 27.384| 128.221
> >
> >
> > Now If hit a key on the telnet session :
> >
> > RTD| 42.203| 67.976| 88.273| 0| 27.384| 128.221
> > RTD| 32.216| 93.427| 128.543| 0| 27.384| 128.543
> > <---------- Here I've hit the key.
> > RTD| 42.203| 68.298| 87.628| 0| 27.384| 128.543
> >
> > And again the calibrator execution results on eliminate the strange
> > behaviour whith the telnet session.
> >
> > Any clues ?
>
> No mystery: hitting a key on a telnet session causes an interrupt
> masking section of 110us, you see it as the maximum if you never
> observed longer masking sections, but it is not the maximum if you
> observed longer masking sections.
OK, but why the masking section on linux side affects to xenomai side ?
Another thing I don't understand is why when the system has load (above
I'm talking about calibrator but the same occurs with dd if=/dev/zero
of=/dev/null), the effect seems to dissapear.
>
> >
> > BTW, if finally the bad numbers on ARM are user-context switches related,
> > are you considering the ipipe upgrading to 2.6.23 ?
>
> No comment. I have already answered this question.
Sorry, I missed the last entries on "High latencies on ARM" from
xenomai-core list.
Regards,
Juan Antonio
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