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Thread: Con Kolivas is working on a new scheduler for Desktop/Multimedia/Gaming PCs

  1. #1
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    Default Con Kolivas is working on a new scheduler for Desktop/Multimedia/Gaming PCs

    (Michael, I hope you will be able to make a frontpage news item out of this one )

    I recently stumbled upon an LWN article that mentioned Con Kolivas is working on a new kernel scheduler for Desktop/Multimedia/Gaming PCs called "BFS":

    http://lwn.net/Articles/350100

    Well, I've tried it. I wrote my experiences with it here:

    http://lwn.net/Articles/350820

    If you're feeling adventurous, you might want to give that one a try. In my case, it helped immensely, especially with sound latency and skips and other artifacts during real-time playback (I was not using an RT kernel before that though). Note that BFS has been updated to 0.205 since I wrote that.

    The patch to kernel 2.6.30 and docs can be found at:

    http://ck.kolivas.org/patches/bfs

    Edit:
    206 was a regression and has been pulled again. If anyone is going to try this, use 205. If you tried 206 (and experienced the extreme stalls) use 205 instead.
    Last edited by RealNC; 09-04-2009 at 10:56 PM.

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    interesting concept good sir. Glad to hear you had a positive experience.

  3. #3

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    If you're feeling adventurous, you might want to give that one a try. In my case, it helped immensely, especially with sound latency and skips and other artifacts during real-time playback (I was not using an RT kernel before that though).
    Maybe you should use RT kernel or you just had messed up config? I have standard Arch Linux kernel (300Hz) and when I benchmark OpenSSL performance (both cores near 100% each) I have no single latency in lmms. I remember you had some problems with ALSA, so it seems problem with kernel config...

    From Con's FAQ: "Because it's designed in such a way that mainline would never be interested in adopting it, which is how I like it."
    EDIT:

    BFS supports NUMA, sorry for confusion....... and while SD was pain I never tried -CK patched kernel.
    Last edited by kraftman; 09-16-2009 at 06:52 AM.

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    Quote Originally Posted by kraftman View Post
    Maybe you should use RT kernel or you just had messed up config? I have standard Arch Linux kernel (300Hz) and when I benchmark OpenSSL performance (both cores near 100% each) I have no single latency in lmms.
    lol. With 300Hz that means you're as perceptive as a turtle. No offense.

  5. #5

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    Quote Originally Posted by RealNC View Post
    lol. With 300Hz that means you're as perceptive as a turtle. No offense.
    Probably I do not notice any latencies (maybe because I'm hardcore turn based strategy gamer ). However, I think some other config options are more important - one time I broke my kernel and even mouse cursor stuttered (everything was to minimize latencies in my feeling, but it behave exactly opposite). Btw. distros should tune kernel, scheduler (CFS should be quite good) to do well on desktops.

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    Lol, good to see Con come back but it sounds like he still is pretty ticked off about the past. From the FAQ:

    Why "Brain Fuck"?

    Because it throws out everything about what we know is good about how to
    design a modern scheduler in scalability.
    Because it's so ridiculously simple.
    Because it performs so ridiculously well on what it's good at despite being
    that simple.
    Because it's designed in such a way that mainline would never be interested
    in adopting it, which is how I like it.
    Because it will make people sit up and take notice of where the problems are
    in the current design.
    Because it throws out the philosophy that one scheduler fits all and shows
    that you can do a -lot- better with a scheduler designed for a particular
    purpose. I don't want to use a steamroller to crack nuts.
    Because it actually means that more CPUs means better latencies.
    Because I must be fucked in the head to be working on this again.
    I'll think of some more becauses later.


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    Heh I like that he included this in the repo:



    So true..

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    Been using it for a week. I don't notice any difference in interactive stuff, but my PC's already fast.

    What I DO notice is that CPU-intensive things (emerge, folding-at-home, etc.) run a hell of a lot faster. I can actually max out all my cores now whereas on CFS I'd always get less than 100%.

    With all due respect to Ingo and Linus, if I can't max out my CPU on a CPU-bound non-interactive program just because of your scheduler, then your scheduler sucks horribly.

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    Quote Originally Posted by Ant P. View Post
    Been using it for a week. I don't notice any difference in interactive stuff, but my PC's already fast.

    What I DO notice is that CPU-intensive things (emerge, folding-at-home, etc.) run a hell of a lot faster. I can actually max out all my cores now whereas on CFS I'd always get less than 100%.

    With all due respect to Ingo and Linus, if I can't max out my CPU on a CPU-bound non-interactive program just because of your scheduler, then your scheduler sucks horribly.
    I noticed that too. For example, a kernel build with "make -j2" now finishes faster than -j2 or -j3 did before. With -j2 I get 100% CPU load now. Before, even with -j8 the CPU load was 95-97%. And the funny thing, even though now load is maxed out, the desktop stays responsive. Before, even if it wouldn't max out the CPU, the desktop would lag.

    Also, another thing is that moving an mplayer window around doesn't result in the video skipping anymore; the video always plays smooth no matter if you move the window or not (just like in MS Windows.)

    However, the Catalyst (fglrx) drivers have problems with this scheduler. OpenGL apps tend to hang and can't be killed. Con suspects a race condition in the Catalyst drivers that are brought forward by the scheduler (as he already suspected and wrote about in the FAQ.)
    Last edited by RealNC; 09-05-2009 at 03:47 PM.

  10. #10

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    It seems bfs is a mess:

    http://marc.info/?l=linux-kernel&m=125227082723350&w=2

    @RealNC

    I really recommend you to try a normal distro (with sane config...), before you post a thing, because it seems you've got something really messed up...

    @Ant P.

    What I DO notice is that CPU-intensive things (emerge, folding-at-home, etc.) run a hell of a lot faster. I can actually max out all my cores now whereas on CFS I'd always get less than 100%.
    Strange, because I have no problems with CPU usage. It seems two Gentoo users have problems.

    @Deanjo

    EDIT:

    Deleted my bull xd

    However, flash problems are flash problems :>
    Last edited by kraftman; 09-16-2009 at 06:58 AM.

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