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Preemptible Linux Kernel: Interviews and Info

Posted by michael on from the patch-and-patch-again dept.

An anonymous submitter sends: "MontaVista and Robert Love are developing a patch for the Linux kernel to make it fully preemptible. Lots of users are involved, and tests show huge reductions in latency. Robert's kernel patches are here. Finally, an interview with Robert, on preemption and more."

3 of 238 comments (clear)

  1. Re:So will that make Linux a superior audio platfo by Starship+Trooper · · Score: 1, Troll
    No, unfortunately. Professional audio processing requires an extremely special form of real-time processing that is pretty much only good for handling audio, and which actually can cause problems with any other types of software. Therefore, it is unlikely that preemption patches for Linux, which must remain a general-purpose system, will be made. Even most Windows professional audio programs don't use Windows' built-in scheduling; they instead take advantage of Windows' rather loose kernel hooks to preempt the operating system and handle real-time scheduling for themselves.

    Look at BeOS for an example of why this sort of processing can't possibly fit into a normal-use system. BeOS was constructed especially for the handling of low-latency media such as audio, but as anyone who tried to program it can tell you, it was exceptionally difficult to program anything other than media apps with it! The extremely high-resolution threading of the operating system made even the simplest programming tasks near impossible, as mutex locks and thread conditionals needed to be spread throughout the code to ensure proper execution. This is why BeOS ultimately flopped: it was too hard to program for.

    But, of course, this is an area where Linux could shine. Due to its open-source nature, a special media-processing fork of the kernel could be made for those who need to deal with real-time audio, while the general-purpose kernel remains general-purpose. In fact, DeMuDi Linux is already striving for this goal.

    --
    Loneliness is a power that we possess to give or take away forever
  2. Windows 2000/NT by Beatlebum · · Score: 0, Troll

    Of course it would be crass to mention that Windows NT/2000 has had a preemptive kernel from day 1. Facts and *nix polictical correctness don't mix too well at /.

  3. Re:So will that make Linux a superior audio platfo by sllort · · Score: 3, Troll

    The extremely high-resolution threading of the operating system made even the simplest programming tasks near impossible, as mutex locks and thread conditionals needed to be spread throughout the code to ensure proper execution.

    Right on! I ran BeOs under VmWare to try developing for it, and the pthreads compatibility was... well let's just be polite and say "extremely non-optimal". The spin locks in the kernel were so tightly placed that any possible race condition you could think of would occur if you didn't mutex lock the hell out of it, and the littany of devices you had to lock to access memory was just unbelievable. I pretty much had to read through the video driver code to get anything done as the documentation got as far as "Hello World" before wishing you luck.

    Anyway, DeMuDi looks to be a step in the right direction - maybe if a Linux distro starts shipping with 2 kernels, a standard kernel and a multi-media enhanced kernel, we'll finally have a workable solution.