Bug 68807

Summary: [snb regression] retuned rc6 values cause power regression
Product: DRI Reporter: nkalkhof
Component: DRM/IntelAssignee: Jani Nikula <jani.nikula>
Status: CLOSED INVALID QA Contact: Intel GFX Bugs mailing list <intel-gfx-bugs>
Severity: normal    
Priority: medium CC: intel-gfx-bugs
Version: unspecified   
Hardware: x86-64 (AMD64)   
OS: Linux (All)   
See Also: https://bugs.freedesktop.org/show_bug.cgi?id=72924
Whiteboard:
i915 platform: i915 features:

Description nkalkhof 2013-09-01 10:02:41 UTC
Hi All,

I've encountered a regression in power consumption on my SNB mobile GT2 using the latest ~danvet/drm-intel-nightly branch. For example during vaapi playback the power drain jumped from approx 11 Watts to 16 Watts. I've tried to reenable power save state for all components using powertop without effect. I also believe I've found the bad commit:

7499671cb211b34322085172c2fbb33ba87825eb drm/i915: tune the RC6 threshold for stability. 

It seems that it takes longer for the GPU to switch to a lower C state resulting in a higher average power consumption.

Could someone take a look at it and confirm please?

Regards
Nic
Comment 1 Daniel Vetter 2013-09-02 08:46:31 UTC
Can you please check with e.g. powertop what the rc6 residency values are for your given workload with and without the offending patch? Just to confirm what's going on.

Chris this smells like a candidate for your patches ...
Comment 2 Chris Wilson 2013-09-02 10:04:52 UTC
So if you apply http://cgit.freedesktop.org/~ickle/linux-2.6/commit/?h=perf (and build with i915.ko builtin), use xf86-video-intel-2.15+ with SNA, and the lastest checkout of intel-gpu-tools, you get not only a new set of *rps* tweaks but also intel-gpu-overlay to show realtime GPU usage and power consumption. I'd be interested in seeing how the rps tweaks interact with your system (for libva, I can only imagine things get worse).


[Not yet integrated into intel-gpu-tools is the ability to record a power usage profile for later analysis - it should be possible through perf, but I haven't finished checking to make sure it works.]
Comment 3 Chris Wilson 2014-03-05 12:03:41 UTC
Poke for updated power measurements.
Comment 4 Jani Nikula 2014-04-10 13:22:38 UTC
Reporter not responding, closing. Please reopen if the problem persists.

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