UIWebView Javascript garbage collection with THREE.js scenes

Question

I'm developing a game with THREE.js that will run inside UIWebView inside an app on iOS8.

I've profiled this application in Chrome's developer tools and ensured that there are no memory leaks - that is - memory use gets up to a certain value and remains constant throughout.

Running this application in UIWebView, however, reveals that the memory use grows over time, as if no garbage collection takes place at all.

I've searched online, but can not determine conclusively whether iOS8 UIWebView has garbage collection or not. Some articles seem to suggest it does, and some that it does not. If it does - how can I trigger this?

The only solution I can imagine at this time, if there is no garbage collection is periodically killing / deallocating UIWebView, and recreating/restarting the app (a game at the menu screen) .

UPDATE:

After spending a few more days looking for leaks here's what I found:

Deallocating UIWebView doesn't work - system never deallocates everything (even with all the suggested hacks) and memory problems get compounded.

I still don't know if UIWebView has mark/sweep garbage collection - the Profile/Instruments panel seems to suggest it does, but the memory use rarely ever goes down. Common sense tells me that some garbage collection must take place, because all the temporary objects in code, and things going out of scope do get cleaned up.

My THREE.js objects do not seem to ever be collected - but this may be related to THREE.js own issues of having to manually dispose of resources (in order to free any GL-related handles etc.)

There are mysterious leaks related to .bind(this) - example setTimeout(object.func.bind(object),100) - will apparently never clean up the function after timeout dispatches - so I end up pre-binding and storing it as a var instead. Same goes for any even handlers passed to jQuery.

My 2 scene game (menu scene and game scene), I ended up rewriting in such a way that both scenes remain in memory (never get removed). Any objects and models I create in the game, instead of relying on GC to get collected, get recycled instead. When objects are removed from the scene, they are put in a pool of objects of the same type to be re-initialized and re-added when such object is required in the scene again. It seemed like an overkill at first, but the benefit is - no memory leaks (objects remain allocated), and faster creation/adding to scene.

Answer 1

The memory grows because some resources are cached in the memory due to HTTP cache strategy. So if the memory does not grow infinitely, don't worry about that.

Answer 2

What you are seeing is probably a bug in iOS8 where the garbage collector never frees up memory. I posted about it here: PhoneGap using way more memory in iOS8 than iOS7

If you can please file a bug with Apple so we can get this fixed in the next OS release.