cx_lowest and CPU usage

[Andriy Gapon]

on 29/01/2008 19:31 Nate Lawson said the following:
> Andriy Gapon wrote:
>> Report for 7.0-RC1 on quite old hardware: 440BX-based motherboard,
>> 450Mhz Pentium III (Katmai).
>>
>> cx_supported claims to support C1, C2, C3. If I set cx_lowest to C3 it
>> immediately gets backed out to C2 with a kernel message about too many
>> short sleeps. But that's not a problem.
>> There is a weird thing: if I change cx_lowest to C2 when the machine is
>> completely idle, top shows that CPU usage for interrupts immediately
>> jumps to almost 20%. Change cx_lowest to C1, CPU usage drops back to
>> almost 0%.
>> Is this normal ?
>> If not, does this indicate some problem in idle routine or is this just
>> incorrect statistics calculation ? Or maybe something with HW ?
> 
> Leave it at C1.  Apparently C2 and C3 don't work on your machine. 
> That's understandable with older, non-laptop hw.
> 

BTW, about C3: it seems that I have PCI_DEVICE_82371AB_3,
PCI_REVISION_4E chip:
intpm0 at pci0:7:3: class=0x068000 card=0x00000000 chip=0x71138086 rev=0x02
hdr=0x00

But for some reason CPU_QUIRK_NO_C3 in acpi_cpu.c doesn't get reflected
in cx_states.

-- 
Andriy Gapon