Crash running OpenGL on iOS after memory warning

Question

I am having trouble with an app with an OpenGL component crashing on iPad. The app throws a memory warning and crashes, but it doesn\'t appear to be using that much memory. Am I

Answer 1

Seeing some code would help, but I can make some gusses:

I have about 40 different models I need to include in my app, so in the interests of memory conservation I am loading the objects (and rendering textures etc) dynamically in the app as I need them. I tried to copy the UIScrollView lazy loading idea. The three 4mb allocations are the textures I have loaded into memory ready for when the user selects a different model to display. (...)

This kind of approach is not ideal; and it's most likely the reason for your problems, if the memory is not properly deallocated. Eventually you'll run out of memory and then your process dies if you don't take proper precautions. It's very likely that the engine used has some memory leak, exposed by your access scheme.

Today operating systems don't differentiate between RAM and storage. To them it's all just memory and all address space is backed by the block storage system anyway (if there's actually some storage device attached doesn't matter).

So here's what you should do: Instead of read-ing your models into memory, you should memory map them (mmap). This tells the OS "this part of storage should be visible in address space" and the OS kernel will do all the necessary transfers when they're due.

Note that Vurforia's ImageTagets sample app also has Uninitialized Texture Data (about one per frame), so I don't think this is the problem.

This is a strong indicator, that OpenGL texture objects don't get properly deleted.

Any help would be appreciated!!

My advice: Stop programming like it was the 1970ies. Today's computers and operating systems work differently. See also http://www.varnish-cache.org/trac/wiki/ArchitectNotes

Answer 2

Odds are, you're not seeing the true memory usage of your application. As I explain in this answer, the Allocations instrument hides memory usage from OpenGL ES, so you can't use it to measure the size of your application. Instead, use the Memory Monitor instrument, which I'm betting will show that your application is using far more RAM than you think. This is a common problem people run into when trying to optimize OpenGL ES on iOS using Instruments.

If you're concerned about which objects or resources could be accumulating in memory, you can use the heap shots functionality of the Allocations instrument to identify specific resources that are allocated but never removed when performing repeated tasks within your application. That's how I've tracked down textures and other items that were not being properly deleted.