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

[Stephen Rothwell <sfr@canb.auug.org.au>]

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