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Novell to Launch Quick-Response Linux

Krishna Dagli writes to mention a C|Net article about Novell's upcoming real-time Suse Linux Enterprise product. From the article: "Real-time operating systems can respond to external events within a guaranteed time frame, a feature that mainstream business computing doesn't generally require but that's necessary for some areas, such as aircraft radar. But in a move that indicates the flexibility of Linux, Novell plans to begin selling the real-time variant of the open-source operating system next month."

69 comments

  1. from the that's-awful-fast dept. by Anonymous Coward · · Score: 5, Insightful

    from the that's-awful-fast dept.

    It could take me a week to respond. As long as I respond within that week and a week is all that's needed, I'm realtime.

    Realtime is not about speed, it's about fixed time intervals.

    1. Re:from the that's-awful-fast dept. by packeteer · · Score: 3, Interesting

      But those fixed time intervals are almost always faster than the lag time you run into from non-realtime OS'es. Windows is of course the clunker we think of first but my linux machine is sometimes not completely responsive and snappy when i clink something.

      --
      unzip; strip; touch; finger; mount; fsck; more; yes; unmount; sleep
    2. Re:from the that's-awful-fast dept. by random+coward · · Score: 2, Insightful

      This isn't true. Those fixed times are almost always slower than the average response time on a non realtime os. The real-timeness adds overhead, thus slower execution and less throughput than a gpos. The only place a real-time system is faster than a general purpose is in the worst case wich is bounded in on the real time os but can be quite large and is usually unknown on a gpos.

    3. Re:from the that's-awful-fast dept. by LiquidCoooled · · Score: 3, Interesting

      Actually, I find windows apps on a stable clean machine to be very responsive, however move to a .net application and they become noticably painful, every action is like a webpage refresh.
      Newer isn't always better.

      --
      liqbase :: faster than paper
    4. Re:from the that's-awful-fast dept. by nomasteryoda · · Score: 1

      Personally, I want my OS to respond in realtime and compute in such a manner. Fixed time intervals? Ok. I get that, but put this way: Would you rather have a figher jet running a realtime OS or die via BSOD? Yeah, that last letter really means Death in this case. realtime computing

      --
      - Good things come to he who waits... but, but Arch Linux FTW!
    5. Re:from the that's-awful-fast dept. by Lisandro · · Score: 5, Informative

      It's actually not a matter of speed. A realtime OS guarantees that a given external event will trigger a response in no more than x milliseconds. This might be slower (or faster) than a non-realtime OS, but it's not the point. There are a lot of applications where things must be attended within a given timeframe (radars, as mentioned, industrial automation, nuclear plant safety devices, etc.). Achieving this this is not a trivial excersice.

      This is not about the response time after you click on your Office document - and in fact, the (huge) added complexity of a RTOS is nor needed nor desired in most desktop and even enterprise uses.

    6. Re:from the that's-awful-fast dept. by Lord_Slepnir · · Score: 1

      It isnt' always faster. A real-time system that uses polling based IO where each application gets, say, a 10ms timeslice every 100ms, might be a bit slower than a non-real time system that uses interrupt-driven IO when the system is under a light load. (interrupt IO is a bit trickier in a real-time OS, since one input can basically spam out every other application).

    7. Re:from the that's-awful-fast dept. by Doctor+Memory · · Score: 2, Informative

      WTF? "real-timeness adds overhead"? The whole point of RTOSes is to remove the overhead and turn almost everything over to the application. Lots of RTOSes have only basic memory management and I/O is largely limited to device discovery and initialization -- everything else is left to the application, because only the application can define how long an operation may take. Some telephone switches can even be rebooted while the applications run!

      You might want to take a couple of computer classes before you post here again.

      --
      Just junk food for thought...
    8. Re:from the that's-awful-fast dept. by yarbo · · Score: 1

      Yeah, figuring out those deadlines is pretty much free, right?

    9. Re:from the that's-awful-fast dept. by Anonymous Coward · · Score: 0

      Good... someone that actually knows what they're talking about. There are already realtime schedulers available for Linux, if you're willing to do a bit of hacking around (and I'd imagine that covers a good many - although not all - of Linux users). What differentiates this from a setup like that - merely the fact that it's prebuilt?

    10. Re:from the that's-awful-fast dept. by Doctor+Memory · · Score: 1

      Figuring out the deadlines is the programmer's job. Code path analysis and worst-case execution time determination are a big part of it. It's all done before the system even boots, so yeah, it's free as far as performance goes.

      --
      Just junk food for thought...
    11. Re:from the that's-awful-fast dept. by MountainLogic · · Score: 1

      RTOS are very much over kill for most RT embedded applications. A good ol' main with an idle loop and interrupts will cover a big chunk of the reeal world. I miss the 6502 - nice hard and clean deterministic interrupts (Thanks Chuck Peddle). OK, there was that issue with http://en.wikipedia.org/wiki/MOS_Technology_6502#D ubious_features simultaneous IRQ and NMI...

    12. Re:from the that's-awful-fast dept. by Jherek+Carnelian · · Score: 1, Insightful

      Figuring out the deadlines is the programmer's job. Code path analysis and worst-case execution time determination are a big part of it. It's all done before the system even boots, so yeah, it's free as far as performance goes.

      Hardly free at all.

      When you have to reinvent the wheel, who do you think is going to produce better average case performance? The guys who have had years to tinker with a variety of implementations of a variety of algorithms and have the flexibility to trade off the occasional pathalogical blip in exchange for improved average case performance, or the guy who has to come up with something in a few months and can't afford a timeline blip even once?

      On one hand you have the design goal of "As fast as possible for as often as possible" and on the other you have a design goal of, "No slower than X, ever." No one has unlimited resources, so of course the results are going to mirror the goals.

    13. Re:from the that's-awful-fast dept. by Doug+Jensen · · Score: 1

      That's not the point, much less the whole point, of RTOSs. You appear to be confusing RTOSs with microkernels and other minimal kernels. And quite the contrary, real-time UNIXs (for example) have more, not less, overhead in the sense that full preemptability (required for minimizing interrupt response times) requires locks which historically have added about 10% extra overhead from the standpoint of throughput. I'm going to save a lot of screen space here by referring you to my web site http://www.real-time.org./ Then maybe YOU won't need to take a couple (real-time) computer classes before you post here again.

      --
      Doug Jensen
    14. Re:from the that's-awful-fast dept. by Doctor+Memory · · Score: 1

      Well, yeah, if you're going to take a general-purpose OS like UNIX and try to make it real-time, you're going to have to deal with the fact that you can't analyze every code path and predict your response time, so you've got to introduce mechanisms to compensate for that. In that case, sure, you've probably got more overhead. The post I was responding to, however, was asserting that a real-time OS would almost always be slower than a general-purpose one. I've worked on a couple of real-time projects, and both of the (microkernal-based) RTOSes we used were much quicker than an equivalent general-purpose OS on the same hardware (I guess that DOS or another single-tasking system might be quicker at a single function, but that's not doing the same work). I suppose you could argue that a microkernal RTOS isn't equivalent to a GP OS, but the OP was asserting that RTOSes in general provided worse response time than GPOSes, which simply isn't true (in my experience).

      --
      Just junk food for thought...
    15. Re:from the that's-awful-fast dept. by Doctor+Memory · · Score: 2, Insightful
      When you have to reinvent the wheel, who do you think is going to produce better average case performance?
      So you're asserting that guys who have worked on a given system for years will produce better average-case performance than some guy on a tight deadline? Well, duh, give the straw man a cigar!

      OTOH, if you're not "reinventing the wheel" but "cranking out a new and improved wheel", and you're the one who has had "years to tinker with a veriety of implementations" (on a variety of projects), then you certainly can produce better average-case performance than some guys whose goal isn't performance but maybe portability, or ease of maintenance, or backwards compatability. Sure, everybody wants their code to run fast, but if your end goal isn't primarily performance, then you won't wind up with the fastest code. Not to mention that real-time work often affords certain conveniences that general-purpose systems don't have. E.g., you can specify that your code will only work with a given CPU / chipset / whatever, so you don't have to go through some generic driver layer that takes your read request and just turns around and passes it through to a driver that may not be fully optimized because it's constrained to support the generic driver interface. There's a lot of abstraction in most GPOSes today, which is unavoidable if you want to be truly "general purpose", but it's anathema to best possible performance.

      Dunno, my first RT experience was a call data collection system running on duplex hardware hooked directly to a phone switch. Each call record represented a "cha-ching!", so we *could* *not* *lose* *any* *data*. We made the hardware as well as the software, and we sweated the details. That's what "real-time" means to me, so maybe it colors my perceptions.
      --
      Just junk food for thought...
    16. Re:from the that's-awful-fast dept. by Doug+Jensen · · Score: 1

      Given the semantics of "quicker" being interrupt response time and the like, my experience is the same as yours: real-time OS's are generally quicker than non-real-time OSs -- I cannot think of a counter-example. Moreover, almost all real-time OSs go to some considerable effort to make "quicker" also be more predictable than interrupt and service call latencies of non-real-time OSs, by which they usually mean least upper bounded (they often thoughtlessly omit the "least" and leave themselves open to upper bounds like the end of the universe). Unfortunately, the usual real-time focus on interrupt response times (i.e., starting tasks fast) suggests there is an implication that this will cause the tasks to complete on time. This implication exists only in the most simple static small scale applications and systems. In general, starting a real-time task quickly (even in zero time) does not imply that the task will complete on time or even at all (I hope it's obvious why that is true).

      --
      Doug Jensen
  2. Quick-Response linux by Eye.Indigo · · Score: 1

    Quick-Response linux ... Whatever happened to accurate headlines

    1. Re:Quick-Response linux by __aaclcg7560 · · Score: 1

      If you want fast headlines, quality is going have to take a hit. Which is why I'm looking forward to a Quick-Response linux.

    2. Re:Quick-Response linux by Eye.Indigo · · Score: 1

      Well it will be neat to have a commercial real-time linux available - a lot of devices have some crappy hacked-up OS inside them. Hopefully that will change now.

    3. Re:Quick-Response linux by poot_rootbeer · · Score: 1


      Indeed. There's a reason why half of this thread is people who misunderstand the nature of an RTOS, and the other half is people helpfully explaining it to the first half, and it's because someone chose to use the phrase "Quick-Response". Shameful.

  3. Is this rtlinux? by rminsk · · Score: 1

    Is this RTLinux from FSMLabs repacked?

    1. Re:Is this rtlinux? by stirfry714 · · Score: 2, Insightful

      Hint: If you actually read the article, it will answer your question.

  4. First Post! by Anonymous Coward · · Score: 0

    Oops, guess I need "Quick-Response Linux," whatever the fuck that is.

  5. Reminds me of Homer as Max Power by Anonymous Coward · · Score: 3, Funny

    Max Power: Kids, there's three ways to do things. The right way, the wrong way, and the Max Power way!
    Bart: Isn't that the wrong way?
    Max Power: Yeah, but faster!

  6. Real time.. by giorgosts · · Score: 1

    With the experience they'll gather from real-time linux, may be they can fix yast which takes forever..

    1. Re:Real time.. by twenex27 · · Score: 1

      Heh.

    2. Re:Real time.. by Sqwubbsy · · Score: 1

      With the experience they'll gather from real-time linux, may be they can fix yast which takes forever..

      Amen. Even on my 64-bit machine, it took minutes to respond. And this was on a fresh install.
      Overall I really like SuSE, but between that and the lack of mpeg support on 64-bit (yeah, I could kludge it - whatever) it was enough for me to keep on keeping on.

      Anyone know why yast is such a pig?

    3. Re:Real time.. by Anonymous Coward · · Score: 0

      use smart package manager http://labix.org/smart. it will download things in parallel, supports multiple mirrors, package dependencies, and additional repositories http://en.opensuse.org/Additional_YaST_Package_Rep ositories, all much faster than yast/zmd whatever they're calling it these days.

  7. Re:That's nothing.. by spacepimp · · Score: 0, Troll

    this is cut n' paste from the BSDnexus forums, from about 15 months ago. i looked around for the industry watchdog mark baron and found nothing but this to reference him. i thought the myth of the smelly hippy coding in his mothers basement had been dispelled. although i bet richard m stallman does put out a mean odor.

  8. Launch Date! by Aditi.Tuteja · · Score: 1

    Novell plans to announce this product at the Gartner Symposium/ITxpo on Oct. 9

  9. Quick Response and Real-Time by postmortem · · Score: 2, Informative

    ...are not related. Real-time operating systems have shadulers that sort tasks per various priorities. Which mean that task admitted with low priority isn't going to have quick response.

    1. Re:Quick Response and Real-Time by just-a-stone · · Score: 1

      you got the point. imho the headline is misleading. real-time is like iso-certification. it just says that things / time stay the same, but it has no qualitative meaning weather it's good / fast or not ;)

  10. Sounds like it might be by soupdevil · · Score: 1

    aimed at military, aeronautics, etc. But it sounds perfect for audio and video production.

    1. Re:Sounds like it might be by aztracker1 · · Score: 1

      Funny, that was the first thing to cross my mind... Audio capture, and multitrack recording controllers, etc. would a good use of such a beast. :)

      --
      Michael J. Ryan - tracker1.info
    2. Re:Sounds like it might be by paulbd · · Score: 2, Informative

      Ingo Molnar and Andrew Morton's original 2.4 patches for better soft-real-time performance were prompted by complaints from those of us in the linux audio (pro-audio/music) software community. Systems like JACK and applications like Ardour were written around this kind of functionality.

      Ingo has picked up the ball and run with it for 2.6 to the point where a kernel patched with his most recent patches is basically hard-time except for cases where a badly written device driver screws it up. And increasingly parts of his work have become part of the vanilla kernel so that even a 2.6 kernel now works pretty well unless you need very low latency (as require for real-time monitoring and FX processing.

    3. Re:Sounds like it might be by temcat · · Score: 1

      How soon do you think will it become unnecessary to patch kernel in order to use Jack and Ardour?

  11. ATTN Novell CIO by njchick · · Score: 4, Funny
    Real-time operating systems can respond to external events within a guaranteed time frame
    Shouldn't Novell's financial department use it? NASDAQ and Wells Fargo will surely appreciate it :)
    1. Re:ATTN Novell CIO by newzabra · · Score: 1

      that is funny man!

  12. Marketting towards aircraft radar? by CounterZer0 · · Score: 2, Insightful

    Give me a break here. Novell is (Barely) known as an enterprise back office company. They make awesome management products, have a decent linux distribution, and a load of magic glue to hold all that together.
    Where in the world does aircraft radar and embedded manufacturing fit into that business model? Is Novell hiring it's competitors to do marketing for it? Eesh!

    1. Re:Marketting towards aircraft radar? by Burz · · Score: 2, Insightful

      Novell needs to diversify, and this looks like a good way to do it.

    2. Re:Marketting towards aircraft radar? by Anonymous Coward · · Score: 1, Interesting

      I work for an aeronautics company that is purchasing this for the real-time capability and the idemnification. I'm sure there are others looking at it as well. Marketing seems to be fine.

    3. Re:Marketting towards aircraft radar? by Anonymous Coward · · Score: 0

      First: the hard realtime kernel is made by Concurrent Computer Corporation, supplier of military simulation goods for more than 30 years. And they do have enough of experience and respect in the simulation and realtime field, before Linux. So you can stop the flame now you got the right information.

      Second: this is aimed at simulation systems, not embedded market, so lets not hink about the toaster running it, think more about small clusters (like 20 computers, connected tru high speed bus, like infiniband.

      Third: the same product is available with redhat distribution

      And now some other general rants about the other answers, as Im not goin to have the patience to answer 5 or 8 times here, one is already driving me crazy:

      - Yes realtime is about fast, no matter how much the theory people like to repeat that its about fixed response time. Nobody is making rtos that answers in 3 minutes, but in 30 microseconds. The most important thing is that it has predictable states of operation. So next time you want to do the "rtos is not necessarily fast zealot", just because you hera that once, read in wikipedia or your engineering teacher told that once, youa re looking silly.

      - Its not RT-Linux kernel. Its another approach. RT-Linux has a dual kernel approach and this kernel (like the WindRiver one) is just one kernel, a linux, patched for low latencya and some other replacements like a different scheduler and some otehr cpu goodies.

      And yes, I have inside information, and I know this product etc etc etc, bla bla bla

      Have fun

  13. Real Time? by CodeMasterPhilzar · · Score: 1

    I'd be happy if they could just help me work out my IPv6 woes between Suse 10.0 and my ISP...

    I too wonder what market they may be going after here...

    Also, I wonder if this will be the usual "jack up Linux and slip a real-time kernel in underneath" approach. Then Linux actually runs as a low(er) priority task on the R-T kernel...

    --
    --- Just another Code-Monkey
  14. Holy smokes!! by Anonymous Coward · · Score: 0

    Quick, to the Linux-mobile!

  15. Comment removed by account_deleted · · Score: 1

    Comment removed based on user account deletion

  16. Bravo, Slashdot commenters by drwho · · Score: 0

    I am happy to see that the majority of people commenting to this article actually are correct when they clarify what Real Time means. This gives me new hope fot Slashdot. Thank you.

    Now, whether or not it's a good business decision for Novell to go down this road is another question.

  17. RTOS overhead... by Junta · · Score: 3, Informative

    A characteristic common of multi-tasking RTOSs is that timeslices are very small, and context switches extremely frequent, to help assure that apps will be able to do something in the required timeline, which is not necessarily a small amount of time, but in many applications it is a short time. There are more complexities, but the bulk of the 'overhead' mentioned in the GP is probably the high percentage of time spent doing context switches rather than useful work. The key word here is multi-tasking RTOSs, you describe cases in which the OS is largely a base for a single application that does everything itself. This is very common in the RTOS world, but their do exist areas where pre-emptive multi-tasking RTOSes fulfill a need....

    Of course, your point is correct too, a requisite step with respect to this particular aspect of a RTOS is generally considered to be doing whatever it takes to make the context switch as fast as possible. In a server or desktop OS historically context switches aren't nearly as optimized as the solution can be for most applications to lengthen the timeslice. Server platforms particularly tend to have long timeslices as their activity isn't highly interactive, and the percentage of the time the system can do useful work is more important than each application being able to do their thing in a timely manner. On a desktop OS, timeslices being shorter is helpful (fairly recently a lot of debate and configurability happened in linux with respect to this), as multiple applications are more directly interacting with users. With a handful of processes it isn't really noticeable but as it scales up the delays get into perceptible fractions of a second. Having a smooth interface is a bit more along the lines of a design point of RTOS, so it makes sense. Anyway, there is a penalty paid, but the timeslices for satisfying human interaction requirements may still be orders of magnitutde higher than those required for RTOS applications, depending on what's going on.

    --
    XML is like violence. If it doesn't solve the problem, use more.
  18. Slow down there, bucko by bozendoka · · Score: 0
    This gives me new hope fot Slashdot.

    The irony! It burns!
    --
    "You will soon be more aware of your growing awareness." - My first recursive fortune cookie!
  19. *shudder* by Schraegstrichpunkt · · Score: 0, Troll
    ... such as aircraft radar

    Linux is good and all, but would you really trust it for critical safety systems? Why not use something that's actually designed for that purpose?

    1. Re:*shudder* by aminorex · · Score: 1

      Ingo Molnar (and others) have been designing Linux to be real-time for many years now. And Novell has elaborated on that work, to provide a packaged system with a large supporting enterprise, which system is specifically designed to be capable of hard real-time operation. What's not to like? Portable code, familiar tools, free as in free... Would you rather trust a closed-source product with 10 engineers reviewing the code, or an open-source one with 10,000 engineers reviewing the code, among them, quite possibly, several of your own hires? Would you rather trust a system that has been deployed in 100 designs, or one deployed in 100,000 designs? Given the free software adoption rates in the engineering community, Linux will quickly become the latter, while QNX and VxWorks will forever remain in a ghetto.

      --
      -I like my women like I like my tea: green-
    2. Re:*shudder* by Anonymous Coward · · Score: 0


      Linux is good and all, but would you really trust it for critical safety systems?
      So you prefer to trust windoze?

      Why not use something that's actually designed for that purpose? Like a purpose written linux/bsd etc kernel?

      Dickhead.

    3. Re:*shudder* by Schraegstrichpunkt · · Score: 1
      Ingo Molnar (and others) have been designing Linux to be real-time for many years now. And Novell has elaborated on that work, to provide a packaged system with a large supporting enterprise, which system is specifically designed to be capable of hard real-time operation.

      Hard realtime and safety-critical are two completely different things, althougth the latter may require the former.

      Would you rather trust a closed-source product with 10 engineers reviewing the code, or an open-source one with 10,000 engineers reviewing the code, among them, quite possibly, several of your own hires? Would you rather trust a system that has been deployed in 100 designs, or one deployed in 100,000 designs?

      Being open-source has absolutely nothing to do with my argument. In safety-critical systems, you want the entire operation of the system to be predictable. That means you might not want preemptive multitasking/multithreading, virtual memory, or really most of what POSIX offers.

      I seriously doubt that "10,000 engineers" are reviewing "100,000 designs" that use Linux as stripped-down as it would need to be to really be appropriate for safety-critical systems. (I doubt that there are even 500 professional engineers who are qualified to work with safety-critical computer systems working on Linux at all, never mind 20 times that number.)

      Linux is simply too complex for safety-critical systems where nearly any bugs are unacceptable. Heck, Linux hasn't even got locally-exploitable security bugs under control, never mind other kinds of bugs. Furthermore, Linux pretty much requires gcc, and gcc has bugs.

      The primary advantage of embedded Linux is reduced non-recurring engineering costs, because it can do a whole bunch of things out-of-the-box that other more specialized systems can't. That's great for most cases, where occasional errors are acceptable, but it's that flexibility (resulting from Linux's complexity) that makes it inappropriate in safety-critical systems.

      I haven't really used QNX or VxWorks, so I can't comment on those, but my understanding is that they're quite a bit simpler than Linux, which is a major benefit for this application. My suggestion (if you need a generic multitasking OS at all) would probably be something small like L4, with a few very well-defined tasks passing messages between each other. If you need to use Linux, run it on a separate machine that communicates with the safety-critical systems, but is not safety-critical itself.

  20. Example uses.. by Anonymous Coward · · Score: 1, Informative

    Passur makes a system system uses Linux with RT patches on the back end for the processing of radar data. About 6 years ago, I helped install and perform low level maintenance for some of the Passur subsystems at IAD for a major carrier there. I also met with and worked with the Passur engineering team near Islip airport in NY and got a day or two of technical training from them. Disclaimer: I have not worked there in over 5 years so my information may be a little out dated.

    The Passur system basically piggy backs off of the airports radar system but is in no way actually connected or related to the airports system. It is 100% passive (hence the name Passur). The unit is "synchronized" and tracks with the airports radar and reads the echoes and bounces from the planes, including the IFF data from the planes. I believe at IAD, the Passur antenna array was at least a mile away from the airports radar too. This data is collated and sent to the airlines or airports tracking system for real time analysis of where planes are and how long until they get to some other point. The data is also sent to Passur for collection for resale to other airline related data companies or smaller airlines that do not have their own systems. The more airports and airlines they have on board using their system, the more data they have and the more useful the data is. Only one system needs to be in place to provide useful data to a much larger area. An example is the DC area, IAD radar can actually serve IAD, DCA, and probably BWI as well.
    When the customer service agent at a gate announces that flight 123 will be arriving in 15 minutes and the monitors around the airport that show flight arrival times are getting that data from a Passur or similar system (or they just make up the times to shut people up).
    You can obviously see that this level of synchronization requires some RT functionality and a lot of initial tuning for the timing.. The Passur system was using this back in 2000 and I have no idea what the actual state of RT Linux was back then but obviously it worked good enough. I believe the main machine was Redhat based.

    One of the advanced functions of this data collection is the ability to record and "play back" what was going on in the air at a certain time as well. Their Islip facility captured the path and data from TWA flight 800 up to the point that it disappeared. I saw that played back when I was there.

  21. Real-time isn't about absolute time frames by ClosedSource · · Score: 1

    "Real-time operating systems can respond to external events within a guaranteed time frame"

    That's not really what real-time is about. Real-time is about consistent timing, not absolute timing. Thus a 100MHZ system can be more real-time than 1GHZ system.

    1. Re:Real-time isn't about absolute time frames by Anonymous Coward · · Score: 0

      lol

      Quote: It is about A
      You: No, it is about A... because A

      Time for a course on logic reasoning?

    2. Re:Real-time isn't about absolute time frames by ClosedSource · · Score: 1

      Sorry, but your A construction dosesn't match the form of my argument. Perhaps you're confused.

  22. please explain by thripper · · Score: 1

    please explain : "Novell plans to begin selling the real-time variant of the open-source operating system next month."

    selling ? support or what ?

  23. Guaranteed-max-response-time is the real issue by billstewart · · Score: 1
    There are lots of RTOS kinds of applications that go for light-weight because they need speed and that's sometimes faster on average and sometimes more reliable. But that's not the critical feature for real-time-ness - it's guaranteed maximum response time, not average speed, usually because the RTOS application is controlling some real-world equipment that needs it. "Going Real Fast" often helps, which is *why* many of the systems are lightweight, but it's not always necessary. Canonical applications include things like aircraft steering or chemical process controls - avoiding the occasional N millisecond latency glitch is much more important than getting average responses in N/10 ms, and that means that the OS kernel has to hand back control often enough regardless of whatever else it might want to do.

    Some telephone switches could also have new operating systems installed while applications are running. Pity that most of them ran on 1970s-80s bit-slice architectures :-) And please don't insult the parent article's poster, because he's right and you're wrong....

    --

    Bill Stewart
    New Fast-Compression-only CPR http://preview.tinyurl.com/dy575ks
  24. Interrupts by seven7h · · Score: 0

    So they made a version of linux with interrupts?

  25. Nope by ClosedSource · · Score: 1

    "So you prefer to trust windoze?"

    Sorry to break it to you, but the OS world is made up of far more than Unix/BSD/Linux and Windows.

    "Like a purpose written linux/bsd etc kernel?"

    No, not at all. If one were to successfully convert a non-realtime OS like Linux into a real-time one, it would essentially be a completely different OS. The same goes for Windows, BSD, UNIX, VMS, etc.

  26. Re:That's nothing.. by Anonymous Coward · · Score: 0

    Wow. That is a large non-cohesive listing of FUD.

  27. not rtlinux by r00t · · Score: 1

    It's a hack that reserves one CPU for real-time tasks. Even the regular kernel stuff gets kicked off that CPU to make room for the real-time.

  28. nope, not the usual by r00t · · Score: 1

    It's instead "reserve one CPU exclusively for real-time". There is no secondary kernel.

    There are some crazy hacks here. Unpatched Linux will run various kernel-related housekeeping tasks on any CPU. With this, no. Other CPUs take care of the one dedicated to real-time.