Bug 212117 - Excessive power consumption in VT
Summary: Excessive power consumption in VT
Status: New
Alias: None
Product: Base System
Classification: Unclassified
Component: kern (show other bugs)
Version: CURRENT
Hardware: Any Any
: --- Affects Many People
Assignee: freebsd-bugs mailing list
URL:
Keywords: patch, vt
Depends on:
Blocks:
 
Reported: 2016-08-24 16:54 UTC by Johannes Lundberg
Modified: 2018-05-06 19:36 UTC (History)
2 users (show)

See Also:


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

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?

https://reviews.freebsd.org/D15302