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. Regards, Juan Antonio _______________________________________________ Xenomai-help mailing list [email protected] https://mail.gna.org/listinfo/xenomai-help
