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

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  • 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, 10:56 PM.

  • kraftman
    replied
    Someone should measure graphic performance, because it's something very important on desktops (yeah, I know, but I believe there will be some games on Linux someday ). In Urban Terror I have double more FPS using CFS scheduler then with BFS (Amarok must be running same time!!! if I run only UT it seems FPS amount is the same). BFS also kills my input sometimes.

    When comes to compilation time BFS does better, but with *Sleepers* disabled in CFS it should be at least as good as BFS. Whatever Phoronix results will be, it seems it won't be fair comparison. BFS "ignores" just too many things which drives to dead input, processes and thus it can be "faster" in some benchmarks. It will be great to see fixed CFS vs more mature BFS results someday.

    P.S. I used generic Arch Linux kernel vs BFS patched kernel from AUR.

    Btw. with NO_NEW_FAIR_SLEEPERS pgbench result is much lower (BFS : CFS : CFS_NNFS using debugfs) - 1650 : 1350 : 935 +/-.
    Last edited by kraftman; 09-13-2009, 01:32 PM.

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  • kraftman
    replied
    Originally posted by deanjo View Post
    That's why it's always good to have alternatives and people "challenging" the system. Chances are if BFS didn't come around regressions (if it is even a regression or it was just broken from the start) probably wouldn't have been addressed in CFS for quite some time.
    Yes, I completely agree. This is great.

    Reading some forums it seems mainly Intel CPUs have those problems. Like RealNC said.
    Last edited by kraftman; 09-13-2009, 11:06 AM.

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  • deanjo
    replied
    Originally posted by kraftman View Post
    The same about CFS. Just some issues had to be fixed
    That's why it's always good to have alternatives and people "challenging" the system. Chances are if BFS didn't come around regressions (if it is even a regression or it was just broken from the start) probably wouldn't have been addressed in CFS for quite some time.

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  • kraftman
    replied
    Originally posted by RealNC View Post
    PS:
    I suppose everyone knows that BFS will not win any benchmarks, right? The Phoronix Test Suite can not benchmark any of the issues BFS tries to solve.
    Actually it can. BFS is "faster" here in pgbech, but I tested CFS in KDE terminal (and NEW_FAIR_SLEEPERS were enabled) and BFS only in vt (DE was not running), because I have some issues with it in graphical environment. There are also problems with BFS like some processes get caught in infinite loops.

    CFS with NEW_FAIR_SLEEPERS disabled should perform better in my opinion. Those problems with compilation times were also addressed.

    That one is actually pretty much the whole point of BFS
    The same about CFS. Just some issues had to be fixed

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  • RealNC
    replied
    Originally posted by StringCheesian View Post
    I've seen rumors of BFS significantly decreasing compile times. Something like "BFS turned a 12 hour compile into 10 hours!!!" - I forget where I saw it.
    This is due to a regression in mainline where CPUs are under-utilized. For example a "make -j2" in dual-core machine only uses about 90% CPU. BFS uses 100% so yes, it finishes faster. Not sure if everyone is affected here.

    He could also do FPS and gtkperf benches with a background process burning cpu, or something like that.
    That one is actually pretty much the whole point of BFS.

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  • StringCheesian
    replied
    Originally posted by RealNC View Post
    Please don't forget to also check with mainline but with NEW_FAIR_SLEEPERS disabled. I assume that kernel debug features will be disabled for benchmarks, so to disable that option you can simply change the default from 1 to 0 in kernel/sched_features.h.

    PS:
    I suppose everyone knows that BFS will not win any benchmarks, right? The Phoronix Test Suite can not benchmark any of the issues BFS tries to solve.
    I've seen rumors of BFS significantly decreasing compile times. Something like "BFS turned a 12 hour compile into 10 hours!!!" - I forget where I saw it.

    He could also do FPS and gtkperf benches with a background process burning cpu, or something like that.

    Leave a comment:


  • RealNC
    replied
    Originally posted by Michael View Post
    BFS benchmarks coming next week off 2.6.31 final.
    Please don't forget to also check with mainline but with NEW_FAIR_SLEEPERS disabled. I assume that kernel debug features will be disabled for benchmarks, so to disable that option you can simply change the default from 1 to 0 in kernel/sched_features.h.

    PS:
    I suppose everyone knows that BFS will not win any benchmarks, right? The Phoronix Test Suite can not benchmark any of the issues BFS tries to solve.

    Leave a comment:


  • L33F3R
    replied
    @Svartalf: Trippppple Kill

    @Michael: Thanks. I eagerly anticipate this 1

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  • Michael
    replied
    BFS benchmarks coming next week off 2.6.31 final.

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