Re: kapm-idled using 45% CPU (why not 100%?)

From: Stephen Rothwell (sfr@canb.auug.org.au)
Date: Sat Mar 31 2001 - 00:44:38 EST

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    Hi Jamie,

    Jamie Lokier <lk@tantalophile.demon.co.uk> writes:
    > Subject says it all. On my laptop which is running 2.4.0, while the
    > machine is completely idle "top" reports kapm-idled as usin about 45% of
    > the CPU. The remaining 55% is reported as idle time.

    This is normal behaviour ... the current implementation of kapm-idled
    means that it is sleeping some of the time, so the real idle process
    actually gets some time. I did a patch a while ago the got the kapm-idled
    up to about 93-95%, but I didn;t think i was all that important.

    > When the machine gets a little more active, the CPU time attributed to
    > kapm-idled decreases while the 55% idle time increases to 85%!

    Again this is normal (although it may not seem sensible).

    > This is not caused be "top": I get the same 45% from "ps -l 3".
    >
    > I remember when kapmd was reporting 100%. Is the new behaviour
    > intentional, and is it saving the maximum power on the laptop?

    I have NEVER seen kapmd getting 100%. You are probably getting
    about as good power saving as you will get (unfortunately) although
    don't hold me to that - I have heard of some laptops that get better
    power savings when CONFIG_APM_CPU_IDLE was NOT set ...

    Cheers,
    Stephen
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