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    SubjectRe: SD still better than CFS for 3d ?(was Re: 2.6.23-rc1)

    * Kasper Sandberg <lkml@metanurb.dk> wrote:

    > Im still not so keen about this, Ingo never did get CFS to match SD in
    > smoothness for 3d applications, where my test subjects are quake(s),
    > world of warcraft via wine, unreal tournament 2004. [...]

    here's an update: checking whether Wine could be a factor in your
    problem i just tested latest CFS against latest SD with a 3D game
    running under Wine: v2.6.22-ck1 versus v2.6.22-cfsv19 (to get the
    most comparable kernel), using Quake 3 Arena Demo under Wine (0.9.41).
    Here are the results in a pretty graph:

    http://people.redhat.com/mingo/misc/cfs-vs-sd-wine-quake.jpg

    or, in text:

    2.6.22-ck1 2.6.22-cfs-v19
    ------------------------ ------------------------
    quake + 0 loops | 41 fps quake + 0 loops | 41 fps
    quake + 1 loop | 3 fps quake + 1 loop | 41 fps
    quake + 2 loops | 2 fps quake + 2 loops | 32 fps
    quake + 3 loops | 1 fps quake + 3 loops | 24 fps
    quake + 4 loops | 0 fps quake + 4 loops | 20 fps
    quake + 5 loops | 0 fps quake + 5 loops | 16 fps

    Quake3-under-Wine behavior under SD/-ck: framerate breaks down massively
    during any kind of load. The game is completely unusable with 1 CPU loop
    running already!

    Quake3-under-Wine behavior under CFS: framerate goes down gently with
    load, gameplay remains smooth. Framerate is still pretty acceptable and
    the game is playable even with a 500% CPU overload. The graph looks good
    and the framerate reduction goes roughly along the expected 1/n
    'fairness curve' - so it all looks pretty healthy. [Note: quake3 keeps
    its fully 41 fps even with 1 competing loop running on the CPU due to
    "sleeper fairness".]

    [ i've re-tested this using other SD and ck versions and other CFS
    versions such as v2.6.23-rc1 and the results are the same. To get the
    fps result i started a simple game scene: Single Player /
    Q3DM1 / I Can Win, turned on the fps display of Quake3, and did not
    move the player at all, just looked at the framerate that is
    displayed. (i also tried other scenes and other gameplay sections and
    they all behave consistently with the above results.) The system was
    otherwise completely idle. While i trust these numbers take them with
    a grain of salt, i'm obviously not neutral in this thing :-) ]

    so Kasper, i'll definitely need your help in tracking down your 3D
    smoothness problem under CFS. I have the feeling that it could be some
    odd factor that only hits your system, and once we've tracked that down
    there will be a simple solution that does not affect the totality of the
    scheduler. So far only you have reported any 3D game smoothness problem
    against recent CFS versions. (all 3D feedback has been positive, and
    that includes a number of gamers as well. Most of the 3D smoothness
    problems were fixed in CFS v13..v15 and it has not been reported to have
    regressed since then.)

    Ingo
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