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=0.4 required=5.0 tests=BAYES_00,FORGED_MUA_MOZILLA autolearn=no autolearn_force=no version=3.4.4 X-Google-Thread: 103376,38d01316d66d8f95 X-Google-NewGroupId: yes X-Google-Attributes: gida07f3367d7,domainid0,public,usenet X-Google-Language: ENGLISH,ASCII Received: by 10.68.227.166 with SMTP id sb6mr415610pbc.4.1331778933157; Wed, 14 Mar 2012 19:35:33 -0700 (PDT) Path: h9ni27310pbe.0!nntp.google.com!news1.google.com!goblin3!goblin1!goblin.stu.neva.ru!eternal-september.org!feeder.eternal-september.org!mx04.eternal-september.org!.POSTED!not-for-mail From: BrianG Newsgroups: comp.lang.ada Subject: Re: Ada and linux real time Date: Wed, 14 Mar 2012 22:35:30 -0400 Organization: A noiseless patient Spider Message-ID: References: <8kb66jddm0qb.1piup0wfaho1$.dlg@40tude.net> <3a01f684-b544-4051-985d-58aab98e832c@v2g2000vbx.googlegroups.com> <13z45jd9irz9x.1j2hj7ayxwkyj.dlg@40tude.net> <5777a4dc-67ef-4a35-b929-653a4d498aac@q11g2000vbu.googlegroups.com> Mime-Version: 1.0 Injection-Date: Thu, 15 Mar 2012 02:35:32 +0000 (UTC) Injection-Info: mx04.eternal-september.org; posting-host="AjcTBPVjSXIOmwAkWmr8nQ"; logging-data="16751"; mail-complaints-to="abuse@eternal-september.org"; posting-account="U2FsdGVkX19ryT5AJWEXK/Q53VNtgaoM" User-Agent: Mozilla/5.0 (X11; U; Linux i686; en-US; rv:1.9.2.24) Gecko/20111108 Thunderbird/3.1.16 In-Reply-To: <5777a4dc-67ef-4a35-b929-653a4d498aac@q11g2000vbu.googlegroups.com> Cancel-Lock: sha1:Mn5PR7mJPPyuxZIQoMM9aofRI+8= Content-Type: text/plain; charset=ISO-8859-1; format=flowed Content-Transfer-Encoding: 8bit Date: 2012-03-14T22:35:30-04:00 List-Id: On 03/08/2012 04:45 PM, slos wrote: > On 8 mar, 13:04, Simon Clubley Earth.UFP> wrote: >> On 2012-03-07, Eilie wrote: >> >>> On 2012-03-07, Dmitry A. Kazakov wrote: >>>> On Wed, 7 Mar 2012 04:10:14 -0800 (PST), slos wrote: >> >>>> I cannot tell for Linux, because I didn't use it for real-time purposes >>>> yet. Ideally it should derive the system time from the TSC. However >>>> scheduling would likely limited when controlled by timer interrupts. The >>>> minimal waiting time is then determined by the timer's period. You should >>>> look for this kernel setting if you want go below 10ms, or what the actual >>>> limit is. >> >>> And what OS do you use for real-time purposes? >> >> Look at RTEMS. It has Ada support built in. >> >> I recommend you read through the online documentation first to decide if >> it's suitable for you. >> >> Start athttp://www.rtems.com/ >> >> Simon. >> >> -- >> Simon Clubley, clubley@remove_me.eisner.decus.org-Earth.UFP >> Microsoft: Bringing you 1980s technology to a 21st century world > > Hi, > > Thank you for your answers. > > I know RTEMS and MarteOS and they are great projects. > > But I want to use the stuff those guys have put in the kernel main > line : > https://www.osadl.org/HOWTOs.howtos.0.html > > It may not be the most accurate or performance may be lower than with > other solutions but I think it would match my needs for now. > Of course, if I can run Ada and get something "real time". > Otherwise, my project is quite useless. > > BR > St�phane I've had a test program similar to what you describe, except I dumped the sequence of times, rather than statistics. I've had it since DOS was the active PC version of GNAT (3.10 or such), and occasionally look at the results on different platforms/versions. From what I've seen, performance on Linux (using standard-out-of-box non-RT versions) varies significantly depending on the distribution. I'd have to look, but I think Knoppix (at the time, maybe 3.6) had surprisingly good results, compared to Red Hat, etc. I assumed it was due the standard background processes they had (or didn't have) running. Of course, my standard test was with a 1 second clock (just a generic timer test, not looking for RT-like performance). I looked at other values, but don't remember the results of small values. -- --- BrianG 000 @[Google's email domain] .com