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    SubjectRe: 2.6 scheduler and "fast user switching"

    Guy wrote:

    >I typically log in as 'root' on the first console. I then invoke
    >fluxbox as the GUI.
    ># XSESSION=fluxbox startx -- :0
    >I then ctl-alt-F2 another console and login as 'user1'. I then
    >invoke KDE as the GUI.
    >$ XSESSION=kde-3.1.4 startx -- :1
    >I may or may not ctl-alt-Fn and login as 'usern' and repeat the
    >Several thoughts:
    >1} I've seen Nick Piggin's suggestion of nicing X server to -10.
    >At the moment, the only way I know to do this is something like
    ># XSESSION=fluxbox nice --adjustment=-10 startx -- :N

    If you're not using my patches then nice causes scheduling latency
    problems so don't do this even if you can. Con's scheduler work actually
    makes interactivity good at the default priority.

    >A} My default security is that only 'root' can perform nice with
    >negative values. I am reluctant to play with security for such a
    >crticial command.

    Debian does this for you. I guess X runs as suid root anyway so
    its not a big security problem.

    >B} All child threads inherit the new nice value. So in the example
    >just above, this means all applications started from the GUI
    >desktop run at a nice value of -10. I believe enhancing the X
    >server nice value this way defeats the purpose of nicing it to
    >begin with. Obviously, despite my readings and attempts at
    >research, I'm must be missing something here.

    Debian manages to only renice the X server. If something like
    this were required in a distro kernel I guess they would do it
    for you nicely.

    >2} I expect to travel down to Florida for Xmass to visit family.
    >One of the things I had hoped to do was to set up my mother's
    >computer as an X server and hang a thin client terminal {read:
    >older PC} off of it. This would allowed my mother and brother to
    >share a reasonably modern system at the same time.
    >This is not me just being cheap. I'm interested in setting up
    >diskless workstations aound a good central X server. I see such
    >setups as appropriate for a number of situations. If the X server
    >requires 'nicing' in a single user environment, what happens in
    >an LTSP environment?

    I think the server runs on the clients... or something ;)

    >My base reference environment is 2.4.20. I still actively use it
    >for everything I do as everything works as expected.
    >Despite my enthusiasm for 2.6, I find it difficult to get
    >everything to 'just work'. I still see problems in the area of
    >nForce based mobos {stupid proprietary nVidia!}, broken BIOSes,
    >and scheduler issues like the above.

    Obviously make sure all your software is up to date with
    Documentation/Changes, and remember we can't help with closed drivers.
    If you still have problems please send in a report. Hope this helps


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