Bug 212117

Summary: Excessive power consumption in VT
Product: Base System Reporter: Johannes Lundberg <johalun0>
Component: kernAssignee: freebsd-bugs mailing list <bugs>
Status: New ---    
Severity: Affects Many People CC: dumbbell, emaste
Priority: --- Keywords: patch, vt
Version: CURRENT   
Hardware: Any   
OS: Any   

Description Johannes Lundberg 2016-08-24 16:54:05 UTC
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

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. 

Comment 1 Jean-Sébastien Pédron freebsd_committer 2018-05-04 21:29:22 UTC

I finally took some time to work on vt(4) performance. My concern was around the input performance (how fast we can write to the console). I didn't do any power consumption measurements, but the patch might help it.

If you have time, could you please try it?

Comment 2 Ed Maste freebsd_committer 2019-12-10 21:22:22 UTC
D15302 has been committed