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    SubjectRe: + restore-missing-sysfs-max_cstate-attr.patch added to -mm tree
    Arjan van de Ven wrote:
    > On Fri, 30 Nov 2007 22:31:17 -0500
    > Mark Lord <lkml@rtr.ca> wrote:
    >
    >> Arjan van de Ven wrote:
    >>> On Fri, 30 Nov 2007 22:14:08 -0500
    >>> Mark Lord <lkml@rtr.ca> wrote:
    >>>
    >>>>> in -mm there is.. the QoS stuff allows you to set maximum
    >>>>> tolerable
    >>>> ..
    >>>>
    >>>> That's encouraging, I think, but not for 2.6.24.
    >>>>
    >>>>> latency. If your app cant take any latency, you should set
    >>>>> those... and the side effect is that the kernel will not do
    >>>>> long-latency C-states or P-state transitions..
    >>>> ..
    >>>>
    >>>> I don't mind the cpufreq changing (actually, I want it to drop in
    >>>> cpugfreq to save power and keep the fan off), but the C-states just
    >>>> kill this app.
    >>>>
    >>>> The app is VMware. I force the max_state=1 when launching,
    >>> ah but then its' even easier... and can be done in 2.6.24 already.
    >>> VMWare after all has a kernel module, and the latency stuff is in
    >>> 2.6.23 and 2.6.24 available inside the kernel already.
    >> ..
    >>
    >> Oh, I'm perfectly happy to write my own kernel module if that's what
    >
    > all you need to do in your kernel module is call
    >
    > add_latency_constraint("mark_wants_his_mouse", 5);
    >
    > or so
    ..

    Dredging up an old regression again now:

    The "make my own module to replace /sys/.../max_cstate" doesn't work
    for the single-core machine we use a lot around here.

    VMware is totally sluggish unless I go to another text window and do this:

    while ( true ); do echo -n ; done

    At which point VMware performs well again,
    the same as with "echo 1 > max_cstate" in 2.6.23.

    Anyone got any suggestions on how to fix this regression
    or work around it for 2.6.24 ?

    Thanks




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