Mailinglist Archive: opensuse-bugs (15732 mails)

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https://bugzilla.novell.com/show_bug.cgi?id=297737

           Summary: Impressive power efficiency possible! (up to 12%)
           Product: openSUSE 10.3
           Version: Alpha 7
          Platform: x86-64
        OS/Version: openSUSE 10.3
            Status: NEW
          Severity: Major
          Priority: P5 - None
         Component: Kernel
        AssignedTo: kernel-maintainers@xxxxxxxxxxxxxxxxxxxxxx
        ReportedBy: funtasyspace@xxxxxxxxx
         QAContact: qa@xxxxxxx
          Found By: ---


Well, I have just played with Intel's PowerTOP tool for some hours to see how
openSUSE 10.3 Alpha 7 behaves according to power consumption.

I tested this on my Lenovo ThinkPad T60p with openSUSE 10.3 Alpha 7 (x86_64)
and KDE 3.5.7 running. I was first a bit disappointed about the 22W - 25W that
powertop told me (with AC unplugged), because I remember having read that
someone managed about 14,7W on his Gentoo system (also on a T60p). 
Next I did the following steps:
- reduced display brightness to minimum
- killed superkaramba
- aticonfig --set-powerstate=1
- disabled WLAN, disabled Bluetooth
- unpluged LAN-cable
- echo 5 > /proc/sys/vm/laptom_mode

After those steps I landed around 18,9W - 19,2W. Well, now I was curious about
the hint PowerTOP was constantly displaying:
"Suggestion: Enable the CONFIG_USB_SUSPEND kernel configuration option.
This option will automatically disable UHCI USB when not in use, and may save
approximately 1 Watt of power."

So I decided to build a modified version of the default kernel by doing a 'make
cloneconfig' and ONLY change the option CONFIG_USB_SUSPEND:
< #CONFIG_USB_SUSPEND is not set
> CONFIG_USB_SUSPEND=Y

I modified the release name (CONFIG_LOCAL_VERSION="-default-usb-suspend") so I
could install the new kernel in parallel with the default one, which was
shipped with Alpha 7. After compiling and installing the new kernel, I booted
openSUSE 10.3 with it and set my system to exactly the same conditions like I
wrote above. Et voila, PowerTOP told me that power consumption drooped to 16,6W
- 16,9W. That's impressive! I double checked these results by booting the
original kernel again, repeating my measurements and then booting the modified
kernel again, repeating my measurements, a second time. The results were
identical with the first run!

Given that, I can verify now, that setting CONFIG_USB_SUSPEND=y reduces power
consumption about 2.3W (= 12%) on my system. Therefore I would recommend
delivering the openSUSE 10.3 default kernel with this option set. As far as I
can tell, I experience no negative side effects with this option set.

PowerTOP recommends setting CONFIG_NO_HZ=y too, but as far as I know, this
option is not available on the x86_64 architecture, yet.

Regards,
Jörg

PS: This is actually an enhancement and no bug, but I set the severity to major
nevertheless, because the effects can really be considered as major ;)


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