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Programming Software Hardware IT Linux Technology

Kernel 2.6 Real-Time Benchmarks 40

Posted by timothy from the shorter-bars-are-better dept.
An anonymous reader writes "This whitepaper at LinuxDevices.com includes benchmarks comparing the real-time performance of the vers. 2.4 and 2.6 linux kernels, based on LynuxWorks' BlueCat Linux 5.0 beta. The graphs compare the results for average and worst-case measurements of both interrupt response and task switch performance for the two kernels, running on a 1GHz Pentium III under relatively heavy load. Check it out -- there's an enormous improvement. The article also includes a rundown of other features of the new kernel that seem likely to be welcomed by embedded developers."
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Kernel 2.6 Real-Time Benchmarks More

Kernel 2.6 Real-Time Benchmarks

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  • Wider Application? (Score:5, Insightful)

    by 4of12 ( 97621 ) on Wednesday September 10, 2003 @08:52AM (#6920153) Homepage Journal

    I'm hoping the benefits of these performance improvements aren't limited to single-purpose embedded devices.

    Better interactive response (framebuffer, keyboard, mouse) would help desktop users, while some of the enterprise warehouse folks could use less interruption of important I/O tasks.

    Maybe those aims can be achieved somewhat by these kernel improvements.

    • Re:Wider Application? (Score:3, Interesting)

      by selderrr ( 523988 )
      i second that. I write software for the psychology dept at our univ, designed to do reaction time experiments. In basic priming experiments, we need accuracy up to at least 3 msec, preferably 1msec. For eye-movement detection I'd like even finer measurements, but under windows that's simply impossible.

      accuracy up to 1msec is feasable by using a sufficiently fast machine (1GHz or more) with enough ram (512 at minimum) and VRAM (64min, more if you want speedy pics), removing network adapters & USB equip

      • Re:Wider Application? (Score:2, Informative)

        by Krunch ( 704330 )
        It seems you need "a system means that performs its functions and responds to external, asynchronous events within a specified amount of time". In other words, a real-time OS. Neither Windows nor Linux are real-time OS. There is some patches [vmlinux.org] that aims at making Linux more real-time.

        You can use Tron too [slashdot.org].
        • I know. I really need an RT OS, but there are 3 reasons why I can't use the RT linux project :

          - the univ has a windows-only network policy. It took me a bucket of sweat just to get authorisation for my OSX tiBook
          - I need to develop an app that is used by 10 people. All of them use windows. Getting them to switch would take more effort than simply making them accept an (occasional) possible 1-5msec delay somewhere in their data.
          - I have 10 years of experience with win32 development, zero years with linux
          • Try Delphi/Kylix from Borland. You can use the same code to compile both win32 and linux apps. Works quite nicely. There's a free (as in beer) version for personal use that you can test - as a university the licenses should also be reasonable.

          • Talk to your computer science department (Score:1, Interesting)

            by Anonymous Coward

            Assumeing you have one, this is a job for your computer science department. They have the people who know how to do this, and you can get plenty of under grads who will work cheap for expirence and their name on a paper.

            A true CS department will also not be so windows focused, and help you fight the IS fools^h^h^h^h^hpeople who insist they know the best way to do your job.

          • the univ has a windows-only network policy.

            Did Microsoft pay them to do this? Was it an overt payment or an under the table bribe?

  • it doesn't say (Score:4, Insightful)

    by Tirel ( 692085 ) on Wednesday September 10, 2003 @08:52AM (#6920154)
    which version they were using exactly.. test2-mm2? test3-ac1? test1? this is supposed to be a serious article?

  • What about the interactivity patches? (Score:5, Interesting)

    by dpilot ( 134227 ) on Wednesday September 10, 2003 @09:17AM (#6920359) Homepage Journal
    The article (Yes, I RTFA.) talks about the responsivness of the new kernel, showing dramatic improvements in active and maximum latencies. Yet at the same time, there are people working very hard on a set of 'interactivity patches' and complaining of skipping when playing music on 2.6.

    I haven't followed those discussions back to the beginning, so I don't know if they're gilding the lilly. But the intense work on interactive scheduling *now* scares me about like the late work on the VM did with the 2.4.0 release.

    Just like the VM was the Achilles heel of 2.4 will interactive response, particularly playing music on a system under load, be the bane of 2.6?

  • May I re-ask the question I asked on Monday? (Score:3, Interesting)

    by Anonymous Coward on Wednesday September 10, 2003 @09:28AM (#6920442)

    May I re-ask the question I asked on Monday [slashdot.org]? And maybe throw in one of my responses for good measure?
    How does this compare with the kernel that was reviewed [and thoroughly trashed] by Dedicated Systems last August?

    NO - I'm not a QNX employee.

    I am, however, about to embark on a huge project that involves real-time collection of massive amounts of biometric data, and I've spent the last several weeks investigating the state of the art of RTOS's.

    We are looking at five possible candidates: VxWorks, Linux, CE.NET, QNX, and LabVIEW Realtime. VxWorks has a lot of market share, but the consensus seems to be that, under the hood, it's a little shaky. The consensus also seems to be that Linux just ain't ready for primetime; in fact, Linux realtime performance is so bad that people believe the kernel will need to be re-written from the ground up before it's ready to play in this league. Don't know much about LabVIEW Realtime, except that the National Instruments salesdroids are happy to sell it to you. QNX looks like it's got the nicest kernel of all, but it's not clear that it's got the driver & third party application support we might need.

    Which leaves us with CE.NET: It's got surprisingly good performance [bests VxWorks in tests], it's got all the multimedia codecs of Windows, and it's got built in support for ActiveDirectory [so technicians could upload data directly into the database and sign their work right then and there].

    On a purely performance-based evaluation, I'd probably choose QNX, but because of its flexibility, we'll probably go with CE.NET.

    Anyway, back to my original point: How is this new 2.6.x "realtime" kernel any better than the 2.4.x "realtime" kernel that failed so miserably in the Dedicated Systems review?

    Again, not trolling - just looking for all the information I can amass.

    Thanks.

    • Taken from the article you reference:

      It has to be said that Red Hat Inc. does not claim any real-time behaviour.

      SO... they compared a RTOS with an (admitedly) non-realtime OS? I'm not surprised at the results.

      RedHat markets ELDS as an OS for embedded systems. Not all embedded systems require realtime performance. Heck, even systems that require realtime performance don't always require the level of performance that QNX can deliver. There's a large number of embedded systems for which even plain Lin

    • Which leaves us with CE.NET: It's got surprisingly good performance [bests VxWorks in tests], it's got all the multimedia codecs of Windows, and it's got built in support for ActiveDirectory Why one would need Active Directory and MS codecs for biometrics data processing real-time system ?

      • Re:May I re-ask the question I asked on Monday? (Score:1, Informative)

        by Anonymous Coward
        Which leaves us with CE.NET: It's got surprisingly good performance [bests VxWorks in tests], it's got all the multimedia codecs of Windows, and it's got built in support for ActiveDirectory Why one would need Active Directory and MS codecs for biometrics data processing real-time system?

        Turns out these medical types are absolutely freakin' paranoid about their double blind tests.

        Think Team A/Team B analysis at the CIA, but in a laboratory setting, it's more like Team A prepares the dosages [placebo ver

    • The Linux kernel was never intented to compete with QNX or any other realtime operating system.
      Try RTAI [polimi.it]. It's a patch to allow hard realtime performance on GNU/Linux systems.
    • You could try LynuxWorks' Bluecat and if that is not good enough they have a true realtime offering, LynxOS, which is ABI compatible with Linux.

  • Beware TCQ on 2.6.0 (Score:4, Informative)

    by tzanger ( 1575 ) on Wednesday September 10, 2003 @09:47AM (#6920618) Homepage

    LKML verified it and I've experienced it personally -- TCQ on IBM Deathstar drives (mine were 60G, the LKML was 120G IIRC) can cause massive fs corruption.

    Apparently a queue depth of 8 (the default it seems) is the specific culprit. LKML seems to say that TCQ of 32 works but I've turned it off entirely now.

    It's marked experimental for a reason. :-)

  • From the whitepaper...

    The QNX NEUTRINO RTOS v6.2 and Embedded Linux Developer's Suite v1.1 were evaluated against the
    same criteria and test suite.

    The QNX NEUTRINO RTOS v6.2 performed very well during this evaluation. None of the performance or stress tests revealed any problems and the RTOS was fast, predictable and reliable at all times. The QNX NEUTRINO RTOS is also the only RTOS that has a true message-based client-server architecture well equipped to handle today's requirements concerning distribute

  • Good Job, SCO! (Score:3, Funny)

    by Anonymous Coward on Wednesday September 10, 2003 @12:57PM (#6922507)
    That is some very fine code.
  • IT ACTUALLY COMPILED ON ALPHA.

    Sorry. I WANTED to test it, but it doesn't work, and I don't know enough to fix it. Something about previous declarations of define's.

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