On 28/01/08 09:51, Juan Antonio Garcia Redondo wrote:
> On 25/01/08 18:00, Gilles Chanteperdrix wrote:
> > On Jan 25, 2008 11:04 AM, Juan Antonio Garcia Redondo
> > <[EMAIL PROTECTED]> wrote:
> > > On 24/01/08 11:02, Gilles Chanteperdrix wrote:
> > > 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.
> >
> > This contradicts what you told us in previous posts. You told us that
> > the maximum latency went up to 130us when starting the calibrator.
>
> I guess that there has been a misunderstanding. In the mail
> https://mail.gna.org/public/xenomai-help/2008-01/msg00108.html I
> wanted to point to the fact that the telnet activity had a direct and
> reproducible efect on lat_max field. So my test was:
> 1) From a minicom terminal run 'latency -t0 -p500'
> 2) From a telnet terminal launch calibrator, kill calibrator etc.
>
> So, the lat_worst numbers I showed in that email has no value. I
> launched the calibrator process during several minutes, and, while I
> was doing the tests I saw the telnet behaviour and I thought that could be
> interesting to report it.
>
> I've done more tests this weekend. I've switched to at91sam9260_ek
> development plattform because I can hold it doing xenomai tests without affect
> my current work.
>
> My numbers:
>
> o Test xenomai-2.4.0 + 5 * (dd if=/dev/sda of=/dev/null) + 5 * (calibrator 180
> 4M calibra) + ping -f -s2048
>
> ./latency -p 500 -t0
>
> RTD| 47.358| 67.976| 93.105| 0| 28.672| 122.422
> RTD| 47.680| 68.298| 91.817| 0| 28.672| 122.422
> RTD| 49.291| 68.298| 91.494| 0| 28.672| 122.422
> RTD| 45.747| 68.621| 90.528| 0| 28.672| 122.422
> RTD| 47.358| 68.621| 90.206| 0| 28.672| 122.422
> RTD| 47.358| 68.621| 91.172| 0| 28.672| 122.422
> RTD| 37.048| 68.621| 92.139| 0| 28.672| 122.422
> RTT| 07:35:22 (periodic user-mode task, 500 us period, priority 99)
>
> >
> >
> > > > 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.
> >
> > It is probably not a masking section on linux side but rather a
> > masking section on I-pipe side. Anyway, the effect does not disappear:
> > it means that the cache effects cause larger latencies than the
> > ethernet interrupt, but maybe I did not understand what you explained.
> > The results you obtain with no load are simply irrelevant.
>
> I'll try to explain it better:
>
> o Without load I run ./latency -t0 -p500.
> RTD| 33.182| 53.479| 67.976| 0| 31.250| 77.319
> RTD| 43.170| 53.479| 67.654| 0| 31.250| 77.319
> RTD| 41.881| 53.479| 67.332| 0| 31.250| 77.319
> RTT| 00:02:07 (periodic user-mode task, 500 us period, priority 99)
>
> o Each time I press a key (over a telnet session) I can see the lat_max field
> increase on 40 to 50 us aprox.
> RTD| 33.505| 53.479| 71.842| 0| 26.739| 77.319
> RTD| 40.592| 62.177| 123.067| 0| 26.739| 123.067
> -------
> \_________: Key pressed
> RTD| 50.579| 53.479| 73.775| 0| 26.739| 123.067
>
>
> o Stop the latency test.
> o run dd if=/dev/zero of=/dev/null
> o run ./latency -t0 -p 500
> RTD| 44.780| 55.734| 89.884| 0| 36.082| 93.105
> RTD| 45.425| 55.412| 89.561| 0| 36.082| 93.105
> RTD| 44.458| 55.734| 90.206| 0| 36.082| 93.105
> RTD| 45.103| 55.412| 90.206| 0| 36.082| 93.105
> RTD| 45.425| 55.734| 88.273| 0| 36.082| 93.105
> RTT| 00:02:07 (periodic user-mode task, 500 us period, priority 99)
>
> o I can't see any effect on lat_max field when I press a key on the
> telnet session.
>
> RTD| 44.136| 55.734| 92.461| 0| 36.082| 94.394
> -------
> \_________: Key pressed
> RTD| 43.814| 55.734| 90.528| 0| 36.082| 94.394
> -------
> \_________: Key pressed
> RTD| 45.103| 55.412| 89.239| 0| 36.082| 94.394
> -------
> \_________: Key pressed
> RTT| 00:03:31 (periodic user-mode task, 500 us period, priority 99)
>
> As you can see the lat_max numbers are under the 100 us while I can go
> up 120 us easily whith the former test.
>
Just to say that the test were done with xenomai-2.4.1 (ipipe 1.8-03).
Regards,
Juan Antonio
_______________________________________________
Xenomai-help mailing list
[email protected]
https://mail.gna.org/listinfo/xenomai-help
