Re: [Powertop] USB devices get wrong power use values

[Marc MERLIN <marc_powertop at merlins.org>]

[-- Attachment #1: Type: text/plain, Size: 1280 bytes --]

On Sun, Oct 13, 2013 at 08:33:51AM -0700, Arjan van de Ven wrote:
> On 9/22/2013 4:54 PM, Marc MERLIN wrote:
> >So, I asked on the linux-usb list, and one thing I quickly found out is that the
> >Watt value given by powertop 2.4 is way off for USB devices:
> 
> what makes you think the value is off?
> 
> >>Power est.  Events/s    Category       Description
> >>   8.18 W    100.0%      Device         USB device: Yubico Yubikey II (Yubico)
> >>   8.13 W    100.0%      Device         USB device: Integrated Camera (Chicony Electronics Co., Ltd.)
> 
> having a USB device active also generally makes the CPU/etc use much more power,
> which Powertop "charges" to the USB device in question.
> 
> 8 Watts sounds entirely reasonable for that to me...

Aah, if the CPU gets involved, then yes, it's a bit more possible.
So, a simple USB keyboard that's unused can keep one core awake and burn 8
watts if something else goes wrong in the kernel to cause that?

Thanks,
Marc
-- 
"A mouse is a device used to point at the xterm you want to type in" - A.S.R.
Microsoft is to operating systems ....
                                      .... what McDonalds is to gourmet cooking
Home page: http://marc.merlins.org/                         | PGP 1024R/763BE901