[Bug 102336] [BYT] Offscreen tests performance drops to <1/3 due to power management

[bugzilla-daemon at freedesktop.org]

https://bugs.freedesktop.org/show_bug.cgi?id=102336

--- Comment #10 from Eero Tamminen <eero.t.tamminen at intel.com> ---
(In reply to Chris Wilson from comment #9)
> (In reply to Eero Tamminen from comment #8)
> > Was the issue BYT specific, like the related perf drop was?

Sorry, I meant the fix.

> The hangs? Haven't seen any, so I don't yet know what's going on there. The
> perf issue here is for byt only (as it is the only one that cannot use the
> HW EI thresholds and so we calculate those manually).

Thans, so it was really BYT specific.  It wasn't clear from the fix
description. :-)


> > When Martin tested modesetting ~1 year ago against Intel DDX, modesetting
> > was same speed or slightly better in 3D cases (and lost in 2D ones).
> > 
> > However, now switching from Intel DDX to modesetting drops onscreen 3D
> > test-cases perf on all platforms for Unigine demos (on anything after BYT),
> > GfxBench test-cases and high FPS cases.
> > 
> > Any idea why?
> 
> Hmm, from my inspection on e.g. Unigine -modesetting was and still is around
> 10% slower.

Good to know.  Interesting that Martin got different results back then.


> As you are very aware, there are so many different factors at
> play -- but under ideal circumstances, the ddx is irrelevant to game
> throughput/latency.

Yea, only think it does it the copy for non-Vsync fullscreen contents and some
Vblank etc synchronization.


> Do you have a specific workload that I can use as an example to see what
> changes may have impacted it?

GpuTest Triangle and SynMark Batch0 are the simplest cases.

Now that I have BXT data, Triangle actually went up on BYT & BXT with
modesetting, although for other tested machines it went down. 

However, the cases I'm more concerned are Unigine tests, because they're low
FPS and therefore the issue looks more like MOCS / tiling issue than just some
(less interesting) high FPS overhead.

I'd suggest checking things either with SKL or KBL (say, GT2).

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