From mboxrd@z Thu Jan 1 00:00:00 1970 Content-Type: multipart/mixed; boundary="===============6081884149619377078==" MIME-Version: 1.0 From: Arjan van de Ven Subject: Re: [Powertop] USB devices get wrong power use values Date: Sun, 13 Oct 2013 11:48:25 -0700 Message-ID: <525AEAF9.5080709@linux.intel.com> In-Reply-To: 20131013162212.GH30504@merlins.org To: powertop@lists.01.org List-ID: --===============6081884149619377078== Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: quoted-printable On 10/13/2013 9:22 AM, Marc MERLIN wrote: >> having a USB device active also generally makes the CPU/etc use much mor= e 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? a bad USB keyboard can keep the processor out of deep package C states.. not a lot the software can do about that... but yet it can be THAT much power delta. (we've seen for example on some servers that a cheap keyboard makes > 15 Wa= tts difference, but measured at the wall socket, so after the power supply/etc) --===============6081884149619377078==--