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Kernel 2.6 Real-Time Benchmarks

Posted by timothy on 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."

6 of 40 comments (clear)

  1. What about the interactivity patches? by dpilot · · Score: 4, Interesting

    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?

    --
    The living have better things to do than to continue hating the dead.
    1. Re:What about the interactivity patches? by oever · · Score: 5, Interesting

      Playing music on a 2.6 kernel is certainly not perfect, especially in the first 30 seconds of a song with xmms. During this time xmms is probably loading the song and the disk access holds back the music stream.

      Performance is, however, much better than with 2.4.

      --
      DNA is the ultimate spaghetti code.
    2. Re:What about the interactivity patches? by irc.goatse.cx+troll · · Score: 2, Interesting

      " 2.4 never skips for me. How can skipping in the first thirty seconds be better than never skipping?"
      They're refering to skipping under load (think compiling a kernel, transcoding video, decompressing large data, etc).

      In 2.6, it skips for the first 30secs before the schedualer can see that its an interactive task.
      In 2.4, it skips until the song is done because the kernel isnt much on caring about 'interactive tasks'.

      --
      Pain lasts, kid. Its how you know you're alive. Sometimes I think this growing up thing is just pain management-TheMaxx
  2. May I re-ask the question I asked on Monday? by Anonymous Coward · · Score: 3, Interesting

    May I re-ask the question I asked on Monday? 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?
    PDF DOCUMENT: http://www.qnx.com/products/ps_neutrino/benchmarks /elds/qnx62_elds.pdf
    **********

    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.

  3. Re:Wider Application? by selderrr · · Score: 2, Interesting

    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 equipment and beefing the process priority up to max.

    But even under those conditions, I occasionally lose a msec here or there. I wonder how OSX behaves under the same conditions...

    --
    When will I end this grieving ? When will my future begin ?
  4. Talk to your computer science department by Anonymous Coward · · Score: 1, Interesting

    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.