From mboxrd@z Thu Jan 1 00:00:00 1970 Date: Mon, 28 Jan 2008 10:21:56 +0100 From: Juan Antonio Garcia Redondo Message-ID: <20080128092156.GA8551@domain.hid> References: <20080123065221.GB6573@domain.hid> <2ff1a98a0801230204s15e4eefaifdd2c946c44549df@domain.hid> <2ff1a98a0801230515i77f8c22bk866c4cd592a3a9b8@domain.hid> <20080124094150.GA7503@domain.hid> <2ff1a98a0801240202g83ca10esd2f7fc928946e3c1@domain.hid> <20080125100404.GA8833@domain.hid> <2ff1a98a0801250900if03294epded12290544d5480@domain.hid> <20080128085123.GA7297@domain.hid> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20080128085123.GA7297@domain.hid> Subject: Re: [Xenomai-help] AT91SAM9260 latency List-Id: Help regarding installation and common use of Xenomai List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , To: Gilles Chanteperdrix Cc: jagarcia@domain.hid, xenomai@xenomai.org 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 > > 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