From mboxrd@z Thu Jan 1 00:00:00 1970 X-Spam-Checker-Version: SpamAssassin 3.4.4 (2020-01-24) on polar.synack.me X-Spam-Level: X-Spam-Status: No, score=-1.9 required=5.0 tests=BAYES_00,FREEMAIL_FROM autolearn=ham autolearn_force=no version=3.4.4 X-Google-Thread: a07f3367d7,8d7b1d8587f412a5 X-Google-Attributes: gida07f3367d7,public,usenet X-Google-NewGroupId: yes X-Google-Language: ENGLISH,ASCII Path: g2news1.google.com!postnews.google.com!g26g2000yqe.googlegroups.com!not-for-mail From: sjw Newsgroups: comp.lang.ada Subject: Re: Task Priorities on Ubuntu Linux Date: Wed, 9 Dec 2009 13:20:30 -0800 (PST) Organization: http://groups.google.com Message-ID: References: NNTP-Posting-Host: 82.30.110.254 Mime-Version: 1.0 Content-Type: text/plain; charset=ISO-8859-1 Content-Transfer-Encoding: quoted-printable X-Trace: posting.google.com 1260393631 19097 127.0.0.1 (9 Dec 2009 21:20:31 GMT) X-Complaints-To: groups-abuse@google.com NNTP-Posting-Date: Wed, 9 Dec 2009 21:20:31 +0000 (UTC) Complaints-To: groups-abuse@google.com Injection-Info: g26g2000yqe.googlegroups.com; posting-host=82.30.110.254; posting-account=_RXWmAoAAADQS3ojtLFDmTNJCT0N2R4U User-Agent: G2/1.0 X-HTTP-UserAgent: Mozilla/5.0 (Macintosh; U; Intel Mac OS X 10_5_8; en-us) AppleWebKit/531.21.8 (KHTML, like Gecko) Version/4.0.4 Safari/531.21.10,gzip(gfe),gzip(gfe) Xref: g2news1.google.com comp.lang.ada:8360 Date: 2009-12-09T13:20:30-08:00 List-Id: On Dec 9, 2:34=A0pm, singo wrote: > Hi, > > Another question on the real-time annex and its implementation in > gnat-4.3 (Ubuntu Linux). > > When I use different task priorities I get an - at least for me - > unexpected behavior... I have defined 10 tasks with different > priority. When I run my program, I expect only one task per processor > (this means four on my quad-core machine) to run. However, > unexpectedly all 10 tasks are run on my machine. > > Is this because the tasks are mapped on the underlying OS (here > Linux), which then instead schedules the tasks of different priority > with some kind of time-slicing (round-robin) approach? I would > appreciate some clarification in this matter. > > Best regards > > Ingo > > P.S: Here comes my example program: > > pragma Task_Dispatching_Policy(FIFO_Within_Priorities); > pragma Queuing_Policy(Priority_Queuing); > > with Ada.Text_IO; > use Ada.Text_IO; > > with Ada.Real_Time; > use Ada.Real_Time; > > procedure TaskPriorities is > > =A0 =A0task type T(Id: Integer) is > =A0 =A0 =A0 pragma Priority(Id); > =A0 =A0end; > > =A0 =A0task body T is > =A0 =A0begin > =A0 =A0 =A0 loop > =A0 =A0 =A0 =A0 =A0Put(Integer'Image(Id)); > =A0 =A0 =A0 end loop; > =A0 =A0end T; > > =A0 =A0Task10 : T(11); > =A0 =A0Task9 =A0: T(12); > =A0 =A0Task8 =A0: T(13); > =A0 =A0Task7 =A0: T(14); > =A0 =A0Task6 =A0: T(15); > =A0 =A0Task5 =A0: T(16); > =A0 =A0Task4 =A0: T(17); > =A0 =A0Task3 =A0: T(18); > =A0 =A0Task2 =A0: T(19); > =A0 =A0Task1 =A0: T(20); > > begin > =A0 =A0null; > end TaskPriorities; It used to be that on Linux you would have to run as root for specified priorities to be respected. FWIW, on Mac OS X Dmitry's program behaves much the same as an ordinary user and as root: variously, $ ./taskpriorities 11 13 12 15 14 18 17 20 19^C $ ./taskpriorities 19 20 18 16 14^C $ ./taskpriorities 19 20 18 17^C $ sudo ./taskpriorities Password: 19 20 18 16 14^C