physics demo performance on android

[metajack]

Currently the physics demo works on desktop and android, but the performance on Android is quite low, although still better than Chrome.

We need to investigate and potentially optimize this.

Note that the framerate counter is offscreen in Servo and can be fixed by adding left: 100px; top: 100px to the #fps rule in the CSS.

[gordonbrander]

Note that the framerate counter is offscreen in Servo and can be fixed by adding left: 100px; top: 100px to the #fps rule in the CSS.

@metajack What about left: 0; top: 0;? The initial location of absolute elements is typically where they would have ended up in the flow. If this does not yet work in Servo, left: 0; top: 0; should pin the counter to the top left which is where it lives on other browsers.

[gordonbrander]

Currently the physics demo works on desktop and android, but the performance on Android is quite low, although still better than Chrome.

If we are constrained by the HW, we can reduce the number of particles, or add a toggle that lets us define a workload size.

[metajack]

@gordonbrander I think the issue with left and top is that left: 0 and top: 0 are under the Android system toolbar, so it can't be seen. That's a bug in Servo we should probably fix.

Also I needed to add --device-pixel-ratio 2.0 to the hardcoded startup args for the G Pad since it's high res.

We hit about 60fps around 25 particles, but we are better than Chrome at most points I measured (1000, 500, 250, 125 and the original 1500). Our performance feels more uneven (lots of 7fps followed by 60fps avging to 20, etc).

[metajack]

@pcwalton discovered that Skia was not being built with ARM NEON optimizations at all. Working on a fix for that.

[metajack]

servo/skia#66

[metajack]

servo/skia#66 has landed, but made little difference in the demos unfortunately. More investigation is needed.

[CYBAI]

Got slow perf with the physics demo on my MBP with latest master (c9229f3).
And the dots even don't move 😂