OS-Wide OpenGL ES Rendering

Although smartphone and tablets still lag behind the technology we have in modern day PCs by several years, their evolution is a highly accelerated version of what we saw in the PC industry. It took decades to go from the first GUIs to the GPU composited and accelerated UIs we have on the desktop today. Android has made a very similar transition in just three years.

Prior to Honeycomb, the majority of screen drawing in Android was done using its skia libraries. These libraries were almost exclusively CPU based and did very little work on the GPU. Over time Google rewrote key elements of Android to use new OpenGL ES rendering paths instead of skia for screen drawing. We saw the first major transition in Gingerbread where parts of the OS became GPU accelerated, but things like the browser were still being rendered to the screen using skia. Honeycomb was a significant step towards GPU accelerated drawing, and ICS all but completes the transition. The other component is the drawing model, which is completely revamped in 3.x and above. 


From Romain Guy's Android Accelerated Rendering Google I/O 2011 Presentation

Honeycomb based tablets were significantly smoother than Gingerbread devices but even they showed some UI performance issues depending on what you asked of them. We later found out that this was a Tegra 2 limitation, something that would surely contribute to NVIDIA not being chosen as the lead SoC partner for ICS.

Also from Romain Guy's Android Accelerated Rendering Google I/O 2011 Presentation

With Ice Cream Sandwich, the OS, browser and all first party apps are OpenGL ES accelerated. The result is absolutely noticeable. App launches, scrolling and window transitions are all buttery smooth. Web browsing is unbelievably smooth and easily comparable to iOS and Windows Phone at this point.

Third party apps have to opt-into the OpenGL ES rendering path, which will likely require an update for those apps that haven't already done so. Google also provides the handy option of forcing all apps to use GPU accelerated apps and ignoring the opt-in (hardwareAccelerated="true" from the AndroidManifest.xml file). The obvious downside is not all third party apps will work gracefully with hardware acceleration enabled, though most do right now. The Southwest Airlines app, for example, will crash as soon as you try to check into a flight if you force GPU accelerated drawing, and Speedtest.net shows a blur for its line graph of throughput during the test. Google has outlined the draw operations that are unsupported in 3.x and 4.x already, which thankfully aren't many. 

 

While it would be nice for Google to allow GPU acceleration settings on a per application basis, the truth of the matter is that many of them work just fine. Those that don't work are likely a simple update away from getting on board, otherwise they risk obsolesce as more platforms get ICS in the future.

If the sluggish UI held you back from Android in the past, ICS almost completely addresses the issue. I say almost completely because there are still some minor hiccups and a couple of more reasonably sized problems with the OS' responsiveness.


Task Switcher with CPU use overlay (new in ICS) enabled

The biggest issue for me is the delay when operating any of the ICS buttons: back, home or the task switcher. While tapping a folder on any of the home screens results in an instantaneous display of its contents, hitting any of the three ICS buttons just isn't as responsive. There's a noticeable delay between when you hit the home button and when you actually appear back at the home screen. It's a delay that's, at least in my opinion, a bit too long. More frustrating is the delay in bringing up the list of recently used apps. It's less than two seconds but it should be in the milliseconds.

I monitored CPU usage while bringing up the task switcher and saw a small spike in CPU usage (~15%) and an associated increase in clock frequency, but nothing significant enough to lead me to believe we're CPU bound here. If anything I wonder if this is a GPU performance limitation similar to what we saw with Tegra 2 and the app launcher on Honeycomb. Given the incredible resolution of the Galaxy Nexus' display and the fact that we're still dealing with a 307MHz PowerVR SGX 540, it's quite possible that the platform just needs a faster GPU. I'm curious to see how well Tegra 3 will do here.

 

The Android vs. iOS Debate The UI: Holo Evolved
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  • Insomniator - Wednesday, January 18, 2012 - link

    I wonder if the Rezound's Adreno 220 will help with the delays using the ICS buttons. Reply
  • tipoo - Wednesday, January 18, 2012 - link

    The chip in this one generally benchmarks right after the Mali 400, the fastest GPU in an Android phone right now. Its probably a software thing, not hardware. Reply
  • Insomniator - Wednesday, January 18, 2012 - link

    According to anand's own benchmarks (can't find much else on the 220) the SGX540 is significantly slower...

    http://www.anandtech.com/show/4243/dual-core-snapd...
    Reply
  • tipoo - Wednesday, January 18, 2012 - link

    I know, but its still one of the faster GPU's out there. I don't see why the GPU would be a limitation on just the function buttons while the rest of the UI is buttery smooth. Reply
  • tipoo - Wednesday, January 18, 2012 - link

    Also, one of the comments below ours show Android 4.03 being faster and almost eliminating that lag, so it was a software thing. Reply
  • doobydoo - Thursday, January 19, 2012 - link

    Fair enough - it may have been a software thing.

    Nevertheless, it's a software thing which doesn't happen on the faster GPU of the Samsung Galaxy S2. So I'd say it's a bit of both.
    Reply
  • zorxd - Friday, January 20, 2012 - link

    Is the iPhone 4 with the slow SGX535 lagging? If not, how can it be a hardware thing? Reply
  • zorxd - Wednesday, January 18, 2012 - link

    You are comparing a 1GHz TI OMAP4 SGX540 to a 1.5 GHz Snapdragon S3 Adreno 220.
    The CPU alone can explain the difference between the Optimus 3D (31 fps) and the qualcom developement platform (37-38 fps).

    As you can see, single core devices using the SGX540 are even slower.

    At a given CPU clock speed (let say the common 1.2 GHz) I think the SGX540 is faster than the Adreno 220.
    Reply
  • jeremyshaw - Wednesday, January 18, 2012 - link

    Different architecture. Snapdragon at 1.5GHz is probably a smidgen slower than Cortex-A9 at 1.2GHz. Remember Snapdragon as an amped-up Cortex A8. Reply
  • french toast - Wednesday, January 18, 2012 - link

    Scorpion is not an amped up A8, they are not related in any way other than the v7 ISA.
    The adreno 220 is way more powerfull than a 540, the problem with it was the poor bandwidth and the terrible drivers qualcomm released it with, it you check out the scores of the samsung galaxy s2 skyrocket with those new drivers it is much faster.
    Reply

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