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> ACPI C-states problem, /proc/acpi/processor/CPU?/power
spoovy
 Posted: Oct 18 2011, 01:49 PM
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I have just been trying to use powertop to reduce the power usage of a file server with an atom cpu. When running powertop though it shows only 2 C-states: C0 and C1. I expected 5 or more C-states shown.

Checking on a laptop running the exact same SL kernel shows the expected result (ie 5 C-states). Going to the /proc filesystem on both systems shows the following differences which illustrate the problem. See the following pastes:

laptop:
CODE

[root@drbunsen ~]# cat /proc/acpi/processor/CPU0/power | grep -i cstate
max_cstate:              C8


server:
CODE

[root@misspiggy ~]# ls /proc/acpi/processor/CPU0/
info  limit  throttling


The file listing C-states available to the kernel doesn't even exist on the server. There are no ACPI - related settings in BIOS except for one to choose the suspend state (between S1 and S3), which I have set to S3.

Any ideas how I can enable C-states on this machine?

Thanks

This post has been edited by spoovy: Oct 18 2011, 01:51 PM


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tux99
 Posted: Oct 18 2011, 04:06 PM
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Which Atom cpu? The desktop Atoms (A and D series) lack most of the power throttling features of the Netbook Atoms.


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spoovy
 Posted: Oct 18 2011, 04:34 PM
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Its the Diamondville Atom 230. It's a desktop model yeah. I assumed they would all have the same features in this regard. huh.gif



This post has been edited by spoovy: Oct 18 2011, 08:02 PM


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tux99
 Posted: Oct 18 2011, 08:05 PM
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QUOTE (spoovy @ Oct 18 2011, 05:34 PM)
Its the Diamondville Atom 230.  It's a desktop model yeah.  I assumed they would all have the same features in this regard.  huh.gif


That cpu has a max TDP of only 4 Watts to begin with, Intel didn't bother to give it low power states, see here:
http://ark.intel.com/products/35635/
CODE
Idle States       No
Enhanced Intel SpeedStep® Technology  No


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spoovy
 Posted: Oct 18 2011, 10:42 PM
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I see. I should've done my research instead of assuming. As usual. I still managed to make some tick reductions using powertop's suggestions though, and as you say at 4W it's not exactly breaking the bank!

Thanks tux99.


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tux99
 Posted: Oct 19 2011, 12:24 AM
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QUOTE (spoovy @ Oct 18 2011, 11:42 PM)
I see.  I should've done my research instead of assuming.  As usual.  I still managed to make some tick reductions using powertop's suggestions though, and as you say at 4W it's not exactly breaking the bank! 

Thanks tux99.


The chipset that goes along with those first gen. desktop Atoms should be your main concern, it has a TDP of 25 Watts!!

Try running X on your fileserver (just switch to runlevel 5 and leave X at the gdm login screen), on some chipsets with integrated graphics running X will switch the GPU to a lower power mode, while if you don't run X the GPU stays in the default high power mode (this is the case for example with my AMD APU based mobo).
Ideally you need a watt-meter for this though, as otherwise you can't tell if running X lowers or increases (could happen too, if the X drivers are badly written) your power consumption.

Some BIOSes allow you to reduce the frequency of the integrated GPU, that should also reduce power consumption. Also disable all peripherals you don't use (serial, parallel port, sound chip) in the BIOS.

First gen. desktop Atoms were really let down by the power hungry chipset, second gen. Atoms are much better in that respect.

Just out of curiosity I would be interested to know how low you can get the power draw (that's if you have a watt-meter to measure it) with your current setup?


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(can be used together with EPEL and ELRepo repositories) - repository mirror: http://linuxsoft.cern.ch/linuxtech/el6/
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spoovy
 Posted: Oct 19 2011, 10:32 AM
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I know the chipset you mean, and fortunately I did read about that batch beforehand so avoided them. Those were very early mobos apparently.
Mine's a more recent build - this is the model - http://www.dell.com/downloads/global/products/optix/en/desktop-optiplex-160-technical-guidebook-en.pdf
Its a SiSM671 Northbridge and SiS968 Southbridge chipset, which is much more reasonable by the looks of it.

I had disabled most ports (4 usb & a serial) and reduced video memory to minimum (64MB i think) which is as low as it'll go; i'll try your other suggestion, and will get back to you when i've finished tweaking, I still hope to get something pretty impressive!


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tux99
 Posted: Oct 19 2011, 12:09 PM
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QUOTE (spoovy @ Oct 19 2011, 11:32 AM)
Its a SiSM671 Northbridge and SiS968 Southbridge chipset,  which is much more reasonable by the looks of it.

Ah ok, that SIS chipset really seems to be much better, 8 Watts TDP according to what I read doing a quick search.


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My personal SL6 repository, specialized in audio/video software: http://pkgrepo.linuxtech.net/el6/
(can be used together with EPEL and ELRepo repositories) - repository mirror: http://linuxsoft.cern.ch/linuxtech/el6/
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