[Bug 212117] Excessive power consumption in VT

bugzilla-noreply at freebsd.org bugzilla-noreply at freebsd.org
Wed Aug 24 16:54:06 UTC 2016


https://bugs.freebsd.org/bugzilla/show_bug.cgi?id=212117

            Bug ID: 212117
           Summary: Excessive power consumption in VT
           Product: Base System
           Version: CURRENT
          Hardware: Any
                OS: Any
            Status: New
          Severity: Affects Many People
          Priority: ---
         Component: kern
          Assignee: freebsd-bugs at FreeBSD.org
          Reporter: johannes at brilliantservice.co.jp

I am concerned that there might be something in VT that are causing high power
consumption.

At login prompt FreeBSD 12-CURRENT on my UP board (Intel Cherryview) the power
consumption is steady at 5W when idle, measured with a watt meter on the 120V
side.

When I do kldload i915kms the power consumption drops to 4W. As comparison,
even running a simple OpenGL app with 60 fps refresh rate in KMS mode does not
cause higher consumption than 4-5W. Starting X brings it up to around ~5W
again.

In /boot/loader.conf I'm loading
zfs
coretemp
acpi_video

CPU is 99.8% idle when running top in from ssh login. 

The watt meter only show whole watts so the difference might not be as big as 1
watt but there definitely is a difference. As someone else said in the mailing
list, the difference is so big in their system it causes the fans to run high
and changing to syscons solved the problem. 

https://lists.freebsd.org/pipermail/freebsd-x11/2016-August/017860.html

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