High power consumption by Intel iGPU on Skylake+
| Affects | Status | Importance | Assigned to | Milestone | |
|---|---|---|---|---|---|
| linux (Ubuntu) |
Confirmed
|
Undecided
|
Unassigned | ||
| Focal |
Confirmed
|
Undecided
|
Unassigned | ||
Bug Description
There is an outstanding regression in i915 that breaks the RC6 power state for Intel iGPUs on Skylake and newer. This bug was fixed upstream in Linux 5.5. I submitted a backport of the fix for 5.4 upstream [1].
My cover letter [2] describes the issue:
The first bug, fixed by "drm/i915/gt: Schedule request retirement when timeline idles" upstream, is very high power consumption by i915 hardware due to an old commit that broke the RC6 power state for the iGPU on Skylake+. On my laptop, a Dell Precision 5540 with an i9-9880H, the idle power consumption of my laptop with this commit goes down from 10 W to 2 W, saving a massive 8 W of power. On other Skylake+ laptops I tested, this commit reduced idle power consumption by at least a few watts. The difference in power consumption can be observed by running `powertop` while disconnected from the charger, or by using the intel-undervolt tool [1] and running `intel-undervolt measure` which doesn't require being disconnected from the charger. The psys measurement from intel-undervolt is the one of interest.
Backporting this commit was not trivial due to i915's high rate of churn, but the backport didn't require changing any code from the original commit; it only required moving code around and not altering some #includes.
[1] https://<email address hidden>/
[2] https://<email address hidden>/
| no longer affects: | lightdm (Ubuntu) |
| no longer affects: | linux |
| description: | updated |
| Ubuntu Kernel Bot (ubuntu-kernel-bot) wrote Missing required logs. | #1 |
| Changed in linux (Ubuntu): | |
| status: | New → Incomplete |
| Changed in linux (Ubuntu Focal): | |
| status: | Incomplete → Confirmed |
| Sultan Alsawaf (kerneltoast) wrote | #2 |
This bug is missing log files that will aid in diagnosing the problem. While running an Ubuntu kernel (not a mainline or third-party kernel) please enter the following command in a terminal window:
apport-collect 1869924
and then change the status of the bug to 'Confirmed'.
If, due to the nature of the issue you have encountered, you are unable to run this command, please add a comment stating that fact and change the bug status to 'Confirmed'.
This change has been made by an automated script, maintained by the Ubuntu Kernel Team.