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    SubjectRe: [ANNOUNCE] BFS CPU scheduler version 0.420 AKA "Smoking" for linux kernel 3.3.0
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    On Tue, 2012-03-27 at 09:30 +1100, Con Kolivas wrote: 
    > On 26 March 2012 00:37, Mike Galbraith <efault@gmx.de> wrote:
    > > Yeah. In all the interactivity testing I've ever done, it's really hard
    > > to not see what you expect and/or hope to see. For normal desktop use,
    > > I don't see any real difference with BFS vs CFS unless I load test of
    > > course, and that can go either way, depending on the load.
    > >
    > > Example:
    > >
    > > 3.3.0-bfs vs 3.3.0-cfs - identical config
    > >
    > > Q6600 desktop box doing a measured interactivity test.
    > >
    > > time mplayer BigBuckBunny-DivXPlusHD.mkv, with massive_intr 8 as competition
    > >
    > > no bg load real 9m56.627s 1.000
    > > CFS real 9m59.199s 1.004
    > > BFS real 12m8.166s 1.220
    > >
    > > As you can see, neither scheduler can run that perfectly on my box, as
    > > the load needs a tad more than its fair share. However, the Interactive
    > > Experience was far better in CFS in this case due to it being more fair.
    > > In BFS, the interactive tasks (mplayer/Xorg) could not get their fair
    > > share, causing interactivity to measurably suffer.
    >
    > massive_intr runs a number of threads that each run for 8ms and then
    > sleep for 1ms. That means they are 89% cpu bound. Run 8 of them and
    > your CPU load is 88.8 * 8 = 7.1. So now you're testing a difficult
    > mplayer benchmark in the presence of a load of 7.1 on a CPU with 4
    > cores. I don't know how much CPU the playback of your particular video
    > is but I suspect it does require a fair amount of CPU based on the CPU
    > it got back in your test. I can virtually guarantee that the amount of
    > CPU BFS is giving to mplayer is proportional to how much CPU is left.
    > Ergo as far as I can see, BFS is likely being absolutely perfectly
    > fair. This sort of fairness equation has been already elucidated in
    > the pHD that I linked to in my original post and he has done a much
    > more thorough analysis than this kind of drive-by test that you're
    > doing and misinterpreting has already shown that BFS is fair to a
    > fault.
    >
    > snip the rest
    >
    > 'top' snapshots are uninteresting because CFS and BFS report cpu time
    > completely differently and a single snapshot tells us nothing.
    >
    > Snip uninteresting-to-desktop-user throughput benchmarks.

    You accuse others of disinterest in their dirty underwear, and wave away
    the wide skid marks in your own with a flick of the wrist. Amazing.

    -Mike



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