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Issue 681835 link

Starred by 2 users
Status: ExternalDependency
Owner: ----
Cc:
█ kbr@chromium.org
dsinclair@chromium.org
Components:
EstimatedDays: ----
NextAction: ----
OS: Android
Pri: 2
Type: Bug



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Webgl Scissor Slow on Mobile

Reported by p...@sketchfab.com, Jan 17 2017 
Steps to reproduce the problem:
1. go to http://osgjs.org/examples/shadowmap/?atlas=1&stats=1
2. check GL FRame Stats for each shadow pass
3. go to http://osgjs.org/examples/shadowmap/?atlas=0&stats=1
4. compare GLFrame stats, and see that using glscissor on a RTT cost FPS a x5 (from 2ms to 10ms)

What is the expected behavior?
Using glscissor should have no impact on perf.
(on dekstop even with intel gpu it doesn't change perf)

What went wrong?
Perf degraded as soon as I used glscissor on my android chrome browser on galaxy S6.

Did this work before? N/A 

Chrome version: 55.0.2883.91  Channel: stable
OS Version: 6.0
Flash Version: Shockwave Flash 24.0 r0

On mobile Tested on Galaxy S6 mobile.
On desktop tested on intel/nvidia win10

Comment 1 by p...@sketchfab.com, Jan 17 2017 

Note: What The sample does is "shadow map rendering" of 3 light in a single shadow map "Atlas" texture when ?atlas=1, thus use scissor to prevent overdrawing "tiles" in the atlas. 
( With ?atlas=0, each texture is a different shadow map, so there is no glScissor calls )

Tried to pinpoint the slowdown, and commenting the glscissor calls is the only thing that does impact the perf in the android chrome mobile galaxy s6 case

Comment 2 by dtapu...@chromium.org, Jan 17 2017

Components: -Blink Blink>WebGL

Comment 3 by kbr@chromium.org, Jan 17 2017

Components: -Blink>WebGL Internals>GPU>Internals
I see no performance difference between the two examples on a Google Pixel.

This is probably a performance bug in the driver or hardware of the Samsung Galaxy S6. Have you tested a different phone?

Comment 4 by kbr@chromium.org, Jan 17 2017

Cc: kbr@chromium.org

Comment 5 by kbr@chromium.org, Jan 17 2017

Labels: GPU-ARM

Comment 6 by p...@sketchfab.com, Jan 18 2017 

Indeed, just tested on Android One plus One and get same performance (like desktop or your pixel). 

Seems to be a the driver or hardware of the Samsung S6 or Mali GPU.

Comment 7 by kbr@chromium.org, Jan 18 2017

Status: ExternalDependency (was: Unconfirmed)
Thanks for testing. I'm going to mark this ExternalDependency. I'll highlight this issue to a couple of issues at ARM and Samsung in case they can work on optimizing their drivers.

Comment 8 by kbr@chromium.org, Jan 18 2017 

Filed internal b/34390489 about this.
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