[Bug 87821] [BYT Bisected] OglBatch1 performance regression ~20%

[bugzilla-daemon at freedesktop.org]

https://bugs.freedesktop.org/show_bug.cgi?id=87821

--- Comment #7 from Eero Tamminen <eero.t.tamminen at intel.com> ---
(In reply to Chris Wilson from comment #6)
> On byt N2820, 1080p:
> 
> dri2: FPS: 99.9493 (MIN: 89.2223, MAX: 123.483, CV: 7.00455%, S: 10)
> dri3: FPS: 58.1767 (MIN: 42.9242, MAX: 66.0809, CV: 8.41218%, S: 10)
> 
> I am not sure if dri3 is being locked to screen refresh or not (max of 66fps
> suggests otherwise, but it is suspiciously close to refresh).

Based on bug 79715 debugging, swaps may be locked to refresh only part of the
time.  Maybe it can get locked also to multiple of 60 FPS.


> Tweaking DRI2 to use async flipping
> [http://cgit.freedesktop.org/~ickle/xserver/commit/?h=async-
> 20141230&id=13372bcf995599b4fe1f427923635d02d2f4c71f]:
> 
> FPS: 138.5 (MIN: 67.0551, MAX: 185.931, CV: 19.661%, S: 10)
> 
> which does support that it is the swap ellision that may be the difference,
> but fwiw I cannot reproduce the reported DRI3 improvements.

Improvements are visible only in memory bound tests and only when they don't
get wrongly refresh locked. Based on bug 79715, on what tests / when DRI3
locking happens, is pretty random. :-)

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