Thanks for the detailed response. My responses are interspersed with yours below. To make them easier to spot I color-coded them.

On 10/15/2014 12:02 AM, Min, Hongbo wrote:
Hi, John

Thanks for your elaborate report. It is very informative! See my comment as below.

-----Original Message-----
From: Crosswalk-help [mailto:[email protected]-
project.org] On Behalf Of John Harrison
Sent: Monday, October 13, 2014 10:15 AM
To: [email protected]
Subject: [Crosswalk-help] stability of Crosswalk across multiple devices for
canvas-heavy app

I recently completed a Cordova app which runs stable and fast on iOS7 and
iOS8 devices. It runs in Webview for Android devices but is slow, so I
migrated it over to Crosswalk. The results were initially promising as
Crosswalk 8  ran fast and stable on the tested device. However, I found the
results were different on other Android devices. After trying 6 different
versions of Crosswalk I finally released the app using Crosswalk 7.36.154.12 as
it seemed the most stable on the tested devices. However, the app is still not
stable on all Android devices I have tested on. Below are my notes for each
version I tried and the results I found on the various devices.
[hmin] The work you did is very helpful for us to continuously improve Crosswalk. Thanks a lot again!

The app manipulates multiple Canvas elements and relies heavily on GPU
hardware acceleration. I'd love to find a way that it might be stable on all
Android 4.x devices using Crosswalk. I'd love some advice as to what I might
try next or what tests might be helpful to the Crosswalk developers.

And...I've tried these Crosswalk versions with every GPU and memory flag
under the sun. Unless I shut off hardware acceleration for the canvas
element or other hardware acceleration (which results in poor performance)
the behavior is the same:

6.35.131.13
 - appeared stable with quick test on LG G3 Android 4.4.2
 - GPU reports only 8MB available on Motorola Droid Mini Android 4.4.4
according to --show-fps-counter. This causes poor performance as the GPU
memory needed is often exceeded. Crosswalk versions 8,9,10 do not have
this problem with this device as these versions report over 100MB of GPU
memory on this same device.
[hmin] In Crosswalk 6, the max available GPU memory is hard-coded to 8MB in GpuMemoryManager, so it doesn't reflect the real number on the device.  See the code https://github.com/crosswalk-project/chromium-crosswalk/blob/crosswalk-6/35.0.1916.17/content/common/gpu/gpu_memory_manager.cc#L81. But from Crosswalk 8, 9, 10, the hard-coded number is changed to 256MB, https://github.com/crosswalk-project/chromium-crosswalk/blob/crosswalk-9/38.0.2125.23/content/common/gpu/gpu_memory_manager.cc#L104. 

Same as Chromium, Crosswalk allows you to force to set the available gpu memory by passing '--force-gpu-mem-available-mb' command line option. With this option, you can instruct Crosswalk to set the total amount of memory that can be allocated for GPU resources when rendering the page. You may want to use this option to increase the amount of gpu memory to see if the performance is improved accordingly.

Since you are using Cordova-Crosswalk to package an app, the usage of command line option is a bit tricky if make_apk.py script is not used. For your information, you can follow the following instructions to add command line options by manual:
1. Create a new empty file named as xwalk-command-line in <assets> folder;
2. Add "xwalk --force-gpu-mem-available-mb=100' to xwalk-command-line file.

Re-package the app using cordova toolchain, and you will get the command line option works.
Testing on Xwalk 7, unfortunately this didn't work. I added in my xwalk-command-line:
xwalk --force-gpu-mem-available-mb=100 --show-fps-counter

I know the command line is being read because the fps counter shows (and does not show if I remove the line). However the amount of memory reported as MAX still is 8MB.



      
 - If wifi/mobile network is not available exhibits strange erratic behavior in
the app. This is in spite of the fact that the app does not use wifi/mobile
network.
[hmin] Do you remember the error message? Is it saying something like "application ... server timeout ..."?
I don't remember the error message, but this was on Xwalk 6 so it might not be worth our time since it does not seem a problem with later versions. If it is helpful to you I can migrate back to Xwalk 6 and catch the error.

      
7.36.154.12 and 7.36.154.13:
 - exact same behavior as 6.35.131.13 except:
  - no issue with wifi/mobile
  - runs but is not stable on LG G3 Android 4.4.2. Erratic crashes. Android log
for crash unknown.
[hmin] If you app is using canvas element, and you also turn on ignore-gpu-blacklist option, it is very possible that the app would crash by accident since it may encounter a bug in gpu driver.
I tried that. The behavior is the same. The only thing that makes the app rock-solid with no crashes is the command line --disable-accelerated-2d-canvas but then the performance is laggy.

      
8.37.189.12, 9.38.208.1, 10.38.219.0
 - app immediately crashes on LG G3 Android 4.4.2. Android log reports GPU
Parse Error 2.
[hmin] Maybe it triggers a bug in gpu driver if ignore-gpu-blacklist.

 - strange delays of up to several seconds at a time on x86 Asus ME302
running Android 4.3. Also is not fully stable (sometimes crashes at erratic
times. Log unknown. Note: app has both x86 and ARM Crosswalk so
Crosswalk is native x86 code, not running in ARM emulator.)
 - GPU reports 100MB available on Motorola Droid Mini, which is stable and
runs fast and well. (Why does this same device report only 8MB available on
Xwalk versions 6 and 7?)
[hmin] The amount reported by show-fps-counter is a number hard-coded by Crosswalk (Chromium), it varies between different versions, see the above explanations. 
There are 2 categories showed in FPS head-up-display: USED and MAX. The USED means that the total bytes allocated for page rendering, while the MAX means the total bytes of GPU memory budgets. Is the 100MB reported by USED or MAX category?
100MB was in the MAX category.

      
The app is built on Cordova 3.6.3-0.2.13 and uses the following plugins:

org.apache.cordova.console 0.2.7 "Console"
org.apache.cordova.device 0.2.8 "Device"
org.apache.cordova.file 1.0.1 "File"
org.apache.cordova.inappbrowser 0.5.2 "InAppBrowser"
org.apache.cordova.media 0.2.12 "Media"
org.apache.cordova.splashscreen 0.3.3 "Splashscreen"
org.apache.cordova.statusbar 0.1.7 "StatusBar"

Thanks in advance for any help,

-John
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