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    Subject[PATCH] kapmd improvent?
    The problem:

    After a burst of heavy load my system (a laptop) returns idle,
    but kapmd isn't scheduled anymore so if I 'top' I can see the system nearly
    100% idle but kampd is consuming 0.0% CPU time.

    The explanation:

    when kapmd returns from schedule_timeout it checks if system_idle(),
    at this point if there is more than one task running we double
    timeout (clamp it to APM_CHECK_TIMEOUT) and go to sleep;
    Q: what if there are tasks that are always
    running when we try to call apm_do_idle ?
    A: we never enter the kapmd inner loop.

    the ?solution?:
    make the timeout short if we find that the system is busy,
    some tries later if the system is idle enough we will enter
    the kapmd inner loop and do some power mgt.

    Alternative solution instead of setting timeout to 1 we could

    timeout >>= 2; /divide by 4
    and clamp the value to 1 if it becomes 0

    So the timeout changes smoothly.

    On my system this makes kapmd come back fast.(without evil side effects, I hope ;) )

    Let me know if this is useful somehow.

    the patch is against vanilla 2.4.9



    --- arch/i386/kernel/apm.c.orig Tue Aug 14 01:39:28 2001
    +++ arch/i386/kernel/apm.c Tue Sep 4 11:02:24 2001
    @@ -1136,8 +1136,10 @@
    - if (!system_idle())
    + if (!system_idle()) {
    + timeout = 1;
    + }
    if (apm_do_idle()) {
    unsigned long start = jiffies;
    while ((!exit_kapmd) && system_idle()) {
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