Bug 100742

Summary:	dpm auto doesn't clock the GPU high enough for SteamVR apps
Product:	DRI	Reporter:	Christoph Haag <haagch>
Component:	DRM/AMDgpu	Assignee:	Default DRI bug account <dri-devel>
Status:	RESOLVED MOVED	QA Contact:
Severity:	normal
Priority:	medium	CC:	fdsfgs, pgriffais
Version:	unspecified
Hardware:	Other
OS:	All
Whiteboard:
i915 platform:		i915 features:

Description Christoph Haag 2017-04-20 21:31:22 UTC

RX 480, Ryzen 1600X, tested on linux 4.10 and linux drm-next-4.12-wip, latest upstream linux-firmware git. Same behavior on both kernels.

I recorded this video, showing umr top, sclk and mclk, while running the simple "Atlas Demo Scene" in the Destinations SteamVR app:

https://www.youtube.com/watch?v=U_mceDSBF7o

With the "auto" setting the GPU power level is not set high enough for SteamVR to render at the Vive's native 90 fps, so reprojection (interpolation to 90 fps) needs to kick in constantly.

Speculation time:
The SteamVR frametime graph shows the purple GPU load from the application ("Destinations") completely below the 11 ms which the application is probably is probably targeting, so dpm has clocked the GPU fast enough for the application to run at 90 fps. But then the application submits frames to the SteamVR compositor which also takes some GPU time and pushes the "total" GPU time taken to render one frame in the app and then display it in the compositor over the target 11 ms time.

Is this correct? Does dpm somehow analyze a per process GPU load? At least in this case the GPU needs to clock fast enough to allow the application + the SteamVR compositor to both render in under 11 ms per frame.

Comment 1 Felix Hellmann 2017-07-04 21:25:25 UTC

I can observe the same behaviour. Setting power_dpm_force_performance_level to high reduces ans smoothes out the StreamVr Compositor frame timings. Even when no "real" app is running (so just the basic space you get when launching)

Arch Linux
RX 480
i7 3770k
4.11.7-1-ck
Mesa git from 2017-07-03

Comment 2 higuita 2017-07-11 21:33:54 UTC

maybe my bug is a dupe from this https://bugs.freedesktop.org/show_bug.cgi?id=101749

i notice that we all have a RX480... does other AMDGPU cards also have this or is the problem only related with this hardware?

Comment 3 Alex Deucher 2017-07-11 22:43:19 UTC

I think we probably need to add a new op to the context ioctl to allow the application to request a floor for a specific clock (sclk, mclk, dclk, eclk, etc.) so that the application can override the natural dynamic selection done by the smu.  Then when commands from that specific context are scheduled, the kernel driver can force a higher floor for whichever clocks are requested.

Comment 4 Christoph Haag 2018-09-09 10:12:22 UTC

The situation has massively improved since I opened this issue at least with very recent kernels. 

I'm hesitant to close it, at least not before doing some testing to see if it can still be reproduced.

Comment 5 Martin Peres 2019-11-19 08:15:32 UTC

-- GitLab Migration Automatic Message --

This bug has been migrated to freedesktop.org's GitLab instance and has been closed from further activity.

You can subscribe and participate further through the new bug through this link to our GitLab instance: https://gitlab.freedesktop.org/drm/amd/issues/157.

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