Messages in this thread | | | Date | Thu, 13 Mar 2008 17:34:37 +0100 | From | Pierre Ossman <> | Subject | Re: [linux-pm] [PATCH] cpuidle: avoid singing capacitors |
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On Wed, 12 Mar 2008 15:11:17 -0400 Len Brown <lenb@kernel.org> wrote:
> > I guess the only way to find out is to disassemble the DSDT. Exposing myself to such concentrations of ACPI is not an appealing project. :/ > > the latest cpuidle code actually publishes the details of the C-states being used. > > $ pwd > /sys/devices/system/cpu/cpu0/cpuidle/state3 > $ grep . * > desc:ACPI FFH INTEL MWAIT 0x20 > latency:17 > name:C3 > power:250 > time:1862590932 > usage:9028970 > > You'll see "desc" change if ACPI pulls a _CST change on you. >
It does not. But my C3 desc looks like this:
state3/desc:ACPI FFH INTEL MWAIT 0x50
What's the meaning of the last number?
I also have different latency and power:
state3/latency:162 state3/power:100
> > Disabling the second core makes the noise go away. This might be a subset of 1., as I've been told that a stopped core enters C1. > > if you disable it at run-time, Linux puts it in C1. > If you never boot it in the first place (eg. maxcpusp=1), the BIOS leaves it in the deepest available C-sate. >
Ah. Didn't know that. I've confirmed this as the noise is there when booting with maxcpus.
> > > > So for now, the only viable workaround is processor.max_cstate.... > > yup, that's why we put it in. Is it insufficient? >
For some value of insufficient. It is sub-optimal. I'm hoping there is a way to enter C3 in a pattern that avoids the noise and still gives a reduced power usage.
Rgds -- -- Pierre Ossman
Linux kernel, MMC maintainer http://www.kernel.org PulseAudio, core developer http://pulseaudio.org rdesktop, core developer http://www.rdesktop.org
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