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Non-Deathmatch: Preempt v. Low-Latency Patch

Posted by timothy on from the floor-wax-and-dessert-topping dept.

LiquidPC writes: "In this whitepaper on Linux Scheduler Latency, Clark Williams of Red Hat compares the performance of two popular ways to improve kernel Linux preemption latency -- the preemption patch pioneered by MontaVista and the low-latency patch pioneered by Ingo Molnar -- and discovers that the best approach might be a combination of both."

12 of 178 comments (clear)

  1. co-op! by FigBugDeux · · Score: 2, Funny

    whats wrong with cooperative multitasking?

  2. Oooooh by NiftyNews · · Score: 4, Funny

    Don't miss the thrilling link to the debate on whether it is PreemptAble or PreemptIble...

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    1. Re:Oooooh by sharkey · · Score: 3, Funny
      Well, let's just make it definitive. Run it through the "CmdrTaco Ofishul Spalchukkar" and let's see what we get:
      • preumtailable
      Well, there...you...go!
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  3. Interrupt priorities by ChaosDiscord · · Score: 4, Funny
    Most RTOS's prioritize device interrupts so that important interrupts ("shut down the reactor NOW!") are serviced first and lower priority interrupts ("time to make the doughnuts") are serviced later.


    Clearly, most RTOS designers have their priorities backwards.



    Mmmm, donuts.

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  4. Re:One good way to reduce kernel latency.. by clone304 · · Score: 4, Funny


    Honestly, I'm not trying to troll you here, but why would you WANT to run a *nix kernel on hardware that's responsible for engine timing? Especially when you apparently already have tech that works. Is the idea just to make vehicles that much harder for people to maintain? The day my mechanic keeps a sysadmin on duty so he patch my buggy Linux 4.5.3 ECU is the day I put a gun to my head and pull the trigger.

    Aside from that. Way to inform the masses.

  5. Re:I did better by (outer-limits) · · Score: 3, Funny

    The only real OS is MVS, aks OS/390 aka Z/OS. It is truly an operating system. It makes no concessions for mere mortals, it is made to run a machine. It hails from 1966. All bow down before it.

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  6. la... by nickynicky9doors · · Score: 2, Funny

    ...tency

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    heuristic algorithm seeks stochastic relationship
  7. Re:One good way to reduce kernel latency.. by Jah-Wren+Ryel · · Score: 2, Funny

    Forget about mechanics. Just let us telnet into the engine and we can fix it ourselves.

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  8. Low-latency and Preemptible on my Notebook by hazzzard · · Score: 3, Funny
    I am using a low-latency kernel on my notebook at the moment and I can report the following behavior:
    • In X (KDE), I can move windows around, load programs, webpages etc. without my MP3-player ever beginning to skip.
    • When doing massive file IO, the MP3-player begins to skip. tar cvzf file.tar.gz bla/ is still ok, but cp -R bla1 bla2 causes massive skipping.
    • When I use the notebook as a samba server, things get worse. Still, massive skpping. Additionally, the samba becomes dog-slow and even the mouse falls asleep.
    • Often times, after such phases of heavy load, the skipping and sound-distortion remains! So I have to reboot the machine from time to time to enjoy music again. Closing the player and opening it again is not enough. Somehow, under heavy load things get messed up enough to make a recovery impossible.
    I did use the preemptive patch before, but performance under heavy load was even worse and the similar problems with rebooting occurred. I was using kernel 2.4.12 for preemptive and I am using kernel 2.4.17 currently. The machine is a Celeron 466 with 128 megs of ram. Still, the low-latency patch makes sense for machines that are primary for playing MP3s and reading emails (that's what my notebook is), but not for desktops with a wider variety of usage patterns. It's just not ready for primetime yet, but it's promising and fun!
  9. Worst of both worlds by Anonymous Coward · · Score: 1, Funny

    To paraphrase the great philospher Hobbs, Linux is theworst of all possible worlds.

  10. Re:No argument here, move along. by Alsee · · Score: 3, Funny

    some misinformed folks have in fact been arguing over "which approach is better"

    They are both wrong. The correct solution is to remodulate the preemption and vent the latency through the Bussard collectors.

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  11. Re:One good way to reduce kernel latency.. by FlyingDragon · · Score: 2, Funny
    The day my mechanic keeps a sysadmin on duty so he patch my buggy Linux 4.5.3 ECU is the day I put a gun to my head and pull the trigger.

    If you use an early development kernel in a production engine, you deserve what you get.