[elrepo-devel] Announcement: kmod-powernow-k8 testing release

[Phil Perry]

Announcing the release of kmod-powernow-k8 in the elrepo-testing repository:

http://elrepo.org/tiki/kmod-powernow-k8

The kmod-powernow-k8 driver provides a patched[1] powernow-k8.ko module 
allowing for per-core power saving on many newer AMD multi-core processors.

[1] We thank Alex/AT his work and for providing a patch to
powernow-k8.ko used herein.


The standard powernow-k8.ko driver in EL5 ties all cores together so all 
cores either run in a full power state or in a power saving state. 
Consequently, much of the time the system is running in a full power 
state and is unable to take advantage of power saving features such as 
CPU frequency throttling or reduction of vCore. This updated driver 
allows each core to be treated independently affording large power 
savings with concomitant reductions in operating temperatures (as 
recorded by k10temp).

Example data below is given for a server based on an Asus M4A78 
pro/Phenom II X4 920 (2.8 GHz), 4x500GB WD HDs and onboard video:

Before installing kmod-powernow-k8, the system was measured drawing 
~150W idle from the wall outlet:

$ uname -r
2.6.18-128.2.1.el5
$ sensors
k10temp-pci-00c3
Adapter: PCI adapter
CPU1 Temp:   +45°C

$ cat /proc/cpuinfo | grep "cpu MHz"
cpu MHz         : 800.000
cpu MHz         : 800.000
cpu MHz         : 800.000
cpu MHz         : 800.000

$ cat /proc/cpuinfo | grep "cpu MHz"
cpu MHz         : 2800.000
cpu MHz         : 2800.000
cpu MHz         : 2800.000
cpu MHz         : 2800.000



and after installing kmod-powernow-k8 we see independently scaled core 
frequencies. The system was now measured drawing ~110W idle from the 
wall outlet giving a *power saving of ~40W (~26%)* and ~9°C temperature 
drop:

$ rpm -q kmod-powernow-k8
kmod-powernow-k8-0.0-2.el5.elrepo

$ sensors
k10temp-pci-00c3
Adapter: PCI adapter
CPU1 Temp:   +36°C

$ cat /proc/cpuinfo | grep "cpu MHz"
cpu MHz         : 2800.000
cpu MHz         : 800.000
cpu MHz         : 800.000
cpu MHz         : 800.000

$ cat /proc/cpuinfo | grep "cpu MHz"
cpu MHz         : 800.000
cpu MHz         : 2800.000
cpu MHz         : 800.000
cpu MHz         : 800.000


It is anticipated that this package will be released to the main elrepo 
repository after satisfactory testing.


Thank you,

The ELRepo Team


Further references:
http://www.centos.org/modules/newbb/viewtopic.php?viewmode=flat&topic_id=20126&forum=39
https://bugzilla.redhat.com/show_bug.cgi?id=502397