From freebsd at godseyfamily.com Sun Jul 30 20:13:47 2006 From: freebsd at godseyfamily.com (David Godsey) Date: Sun Jul 30 20:13:49 2006 Subject: Information Sites Message-ID: <3945.71.213.169.51.1154290426.squirrel@godseyfamily.com> So I have been combing the internet for information on realtime FreeBSD, but the information is limited. So there must be some more information out there, but I do not know where to look. Can someone direct me please? A positive attitude may not solve all your problems, but it will annoy enough people to make it worth the effort. If there are no stupid questions, then what kind of questions do stupid people ask? Do they get smart just in time to ask questions? David Godsey From arne_woerner at yahoo.com Sun Jul 30 21:11:41 2006 From: arne_woerner at yahoo.com (R. B. Riddick) Date: Sun Jul 30 21:11:43 2006 Subject: Information Sites In-Reply-To: <3945.71.213.169.51.1154290426.squirrel@godseyfamily.com> Message-ID: <20060730211140.24074.qmail@web30310.mail.mud.yahoo.com> --- David Godsey wrote: > So I have been combing the internet for information on realtime FreeBSD, > but the information is limited. So there must be some more information > out there, but I do not know where to look. Can someone direct me please? > Hmm... I do not have practical experience in real time operations (just my mostly theoretical studies of task scheduling and control engineering), so I can only hope my contribution is not too useless/stupid... :-) I say, have u read the man page rtprio(2) and polling(4)? I would guess, that u might want to set kern.clockrate to something high (1000..2000) (e. g. via /boot/loader.conf's kern.hz). Furthermore I would recommend, that u do some tests/research/experiments in ur specific environment (remember: real time constraints can be very different (e. g. a simple electronic calculator is ok, when u just want to compute the taxes in a shop or in a restaurant, but when u want to compute the course of Cpt. Picard's Enterprise (StarTrek) u would need something faster (or it might get struck by some kind of lightning or get stuck in a sun))). In this case here it is the question, if u can tolerate fluctuations in scheduling accuracy (response time) due to voluntary/unpredictable/dynamically-scheduled kernel activity (I think polling(4) could just help (a little) with network devices, so that hard disc activity can still hinder real time tasks). >From the point of view of digital control engineering operating systems like *BSD are no real real-time operating systems... Real real-time operating systems are obviously able to guarantee a very high scheduling accuracy... I just did this litte experiment with (avg. about 1.3Mbit/sec, peak about 16Mbit/sec) disc traffic at the same time and a clock rate of 1000Hz: > rtprio rtprio: normal priority > repeat 10 time sleep .2 0.007u 0.015s 0:00.22 4.5% 12+396k 0+0io 0pf+0w 0.000u 0.030s 0:00.23 13.0% 182+1332k 0+0io 0pf+0w 0.000u 0.032s 0:00.23 13.0% 181+1288k 0+0io 0pf+0w 0.010u 0.021s 0:00.23 13.0% 276+2064k 0+0io 0pf+0w 0.006u 0.026s 0:00.24 8.3% 144+1230k 0+0io 0pf+0w 0.000u 0.029s 0:00.23 8.6% 136+966k 0+0io 0pf+0w 0.000u 0.032s 0:00.24 12.5% 185+1420k 0+0io 0pf+0w 0.021u 0.010s 0:00.24 12.5% 182+1332k 0+0io 0pf+0w 0.006u 0.025s 0:00.28 7.1% 278+2130k 0+0io 0pf+0w 0.008u 0.026s 0:00.24 8.3% 276+2064k 0+0io 0pf+0w neo# rtprio 30 -$$ neo# rtprio rtprio: realtime priority 30 neo# repeat 10 time sleep .3 0.000u 0.025s 0:00.33 6.0% 138+1018k 0+0io 0pf+0w 0.000u 0.028s 0:00.33 6.0% 276+2036k 0+0io 0pf+0w 0.000u 0.027s 0:00.33 6.0% 140+1084k 0+0io 0pf+0w 0.000u 0.028s 0:00.33 6.0% 138+1018k 0+0io 0pf+0w 0.006u 0.024s 0:00.32 6.2% 412+2988k 0+0io 0pf+0w 0.000u 0.026s 0:00.32 6.2% 138+1018k 0+0io 0pf+0w 0.006u 0.020s 0:00.47 4.2% 274+1970k 0+0io 0pf+0w 0.006u 0.019s 0:00.32 3.1% 552+4072k 0+0io 0pf+0w 0.000u 0.013s 0:00.31 3.2% 276+2036k 0+0io 0pf+0w 0.000u 0.014s 0:00.31 3.2% 276+2036k 0+0io 0pf+0w -Arne __________________________________________________ Do You Yahoo!? Tired of spam? Yahoo! Mail has the best spam protection around http://mail.yahoo.com From freebsd at godseyfamily.com Mon Jul 31 22:02:20 2006 From: freebsd at godseyfamily.com (David Godsey) Date: Mon Jul 31 22:02:23 2006 Subject: Point in the right direction Message-ID: <58304.134.253.26.6.1154383337.squirrel@godseyfamily.com> So I have been combing the internet for information on realtime FreeBSD, but the information is limited. So there must be some more information out there, but I do not know where to look. Can someone direct me please? A positive attitude may not solve all your problems, but it will annoy enough people to make it worth the effort. A positive attitude may not solve all your problems, but it will annoy enough people to make it worth the effort. If there are no stupid questions, then what kind of questions do stupid people ask? Do they get smart just in time to ask questions? David Godsey