Messages in this thread |  | | Subject | Re: kapm-idled Funny in 2.4.10-ac12? | Date | Fri, 12 Oct 2001 19:08:52 +0100 (BST) | From | Alan Cox <> |
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> I am having almost the same problem in 2.4.12-ac1: > > gallir@linux:~$ uname -a > Linux linux 2.4.12-ac1 #2 Fri Oct 12 19:01:03 CEST 2001 i686 unknown > > kapm-idled consumes a 14% of CPU (in a P3 1GHz) > > PID USER PRI NI SIZE RSS SHARE STAT %CPU %MEM TIME COMMAND > 3 root 17 0 0 0 0 RW 14.3 0.0 1:17 kapm-idled > > The same happens with vanilla Linus tree (tested up to 2.4.11). In a P2, > CPU consuption was more than 85%. > > The CPU's temperature, while the system idle, is more than 4 degrees (C) > higher than the same conditions with the kapm-idled disabled.
I've been reading throught the APM spec and code a bit further. The more I read the more I wonder quite how our idle code is meant to work and what kind of beer was overconsumed during its writing.
There are two glaring issues I can see right now
#1 The BIOS might sleep for a tick, but it is also is allowed to slow the cpu and return straight back to us.
If it returns back to us we spin in a tight loop at the lower clock speed calling the APM bios. Not ideal.
Just fixed that in my tree for the next -ac
#2 We test system_idle() nr_running==1, but we spent all our time pretending we aren't running. Im not 100% sure the test is safe yet
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