Possible excessive (video) memory crash on iPad 1 but not 3GS?

bakedbeing wrote: First up, thanks to the team for AIR 2.6! It works unbelievably well for such young (on IOS) software! We have quite a graphically rich game in development and have had a lot of success with the 3GS, iPhone 4 and iPad 2. On the iPad 1 however, we're getting an intermittent screen blackout followed by a crash back to the operating system. We're getting no flash error and no crash log. The 3GS and the iPad 1 have the same amount of memory, and the app is crashing sometimes while using 7 MB (according to Doob Stats) and sometimes when using 14 MB, so it's not consistently a memory problem. What is consistent however is that it crashes while putting rich menus on screen while lots of bitmaps (tiles) for our level are in memory. The iPad has unified memory usage (system and GPU ram are served by the 256MB) but a much bigger display area, so our thought is that it's probably the video memory being slammed by details, rich menus (with transparent PNGS) appearing and sucking up video ram while we still have level tiles in memory. Our game's complete and submitted for iPhone so far, and there's a limited amount we can do about the png graphics in a tight iPad conversion turnaround period, so we're endeavouring to learn all we can about the AVM and video memory on the iPad. We have a few questions: 1: Can running out of memory cause an app to black out and crash without any warning/explanation? 2: Is there any way to profile video memory usage on the iPad? Any way at all to keep tabs on the video memory? 3: Is there any way in AIR to listen for the iOS low memory warning? In Objective C they implement the applicationDidReceiveMemoryWarning handler function. 4: What's best practise on loading bitmaps? Will calling the myBitmap.bitmapData.dispose() function explicitly clear up video memory? 5: Will AIR 2.7 have any notable changes in usage of video memory? 6: Any other solutions in mind? Thanks everyone!

I've had exactly the issue that you describe and the solution is relatively painless. (that is if it is caused by the same coding practice I was doing)

answers

1. Yes definately this can happen. I've even crashed the OS with my own bad code.

2. iPad has unified system and video memory. Unlike android there is no reliable way I know of to peak into what the OS thinks what memory is being used for what.

3. Don't think so sorry

4. When you are done with a bitmap it is very important that you call the dispose method on it and also it isn't a bad idea to invoke System.gc()

so:

removeChild(yourBitmap);

removeEventListener(whateverListener.WHATEVER, yourFunction);

yourBitmap.dispose()

System.gc()

5. I don't think there are any major changes but if you can go with 3.0, it is better in a lot of ways

6. No other solutions. I think you are on the right track with the dispose method. It is strange to me that it is not required to dispose bitmap data inside of premade MovieClips. Raw bitmaps will get you in trouble if you don't dispose of them in a timely matter. Unfortunately we can't be as wasteful with memory on iOS as we can be on Windows. It will be a while before there are 2 gigabyte iPads.

You can test this issue for yourself on a new movie. Have a movie spawn 100 fullscreen bitmaps one at a time over a number of frames. I bet you won't get more than 60 loaded without disposing the previous ones.

Unfortunately I don't have a solution for you, except to test out CPU mode if it performs well enough for you.  We also tried to use GPU mode for our app and iPad 1 would often crash after sustained play. Xcode Instruments revealed that allocated memory was constantly creeping up until the critical point where the crash would occur.  Using (AIR 2.7) CPU mode fixed the problem and memory usage was rock solid.  

The CPU mode performance is not as great but it sufficed for our application. I never found out exactly what caused the issue in GPU mode.

i have apps running just fine on 3GS, 4, iPad 2 and crash all the time on iPad 1 (and 3G)

always a memory problem

i'm surprised you haven't got crash logs

have you looked at the Xcode console?

I am  experiencing this same problem -- my app (AIR 3.1/GPU mode) frequently crashes as described by bakedbeing on the iPad1 but is stable on iPad2 and iPhone 3GS/4/4S.

The question remains unanswered:

"2: Is there any way to profile video memory usage on the iPad? Any way at all to keep tabs on the video memory?"

Per sanika, "iOS can kill your application if it is using too much memory". What, exactly, in terms of bytes, constitutes "too much memory"? Exactly how much memory, in terms of bytes, is actually available? Is there a difference between the amount of memory available to the CPU and to the GPU, or is this shared? Is AsterLUXman's theory true that garbage collection calls take longer to execute than calls which fill up GPU memory executed in the same cycle, causing these crashes? If so, is there some way to poll the amount of memory that is actually available? Considering that the crashes occur long before reaching the device's 256MB limit, is there some limit to the amount of memory that can be allocated by a single call?

Apologies if these are noob questions.

Hi,

iOS can kill your application if it is using too much memory, which is what seems to be happening in your case. It is not possible for an AIR application to listen for applicationDidReceiveMemoryWarning and handle it.

As far as best practices are concerned, I can suggest the following, you might already be using them:

1) Removing event listeners,

2) Using the correct display objects - work with bitmap and use sprite if you need it etc.

3) Avoid using filters if you can.

4) If you are setting CacheAsBitmap, you should set i to true in the lowest leafs in the display list, and not on a container that has constantly moving children.

AIR 2.7 does have significant rendering improvements in CPU mode.

Hope it helps,

Sanika