Keeping RAM usage small for iOS Notification Service Extension

For an iOS NSE the total memory limit is 24MB. Trying to use some of my Haxe code blows this limit almost immediately, with 15MB being held by the hxcpp GC in 15 1MB allocations, according to the Xcode memory profiler.

I really doubt the code in question actually needs 24MB of memory, but probably this is the result of a lot of garbage being generated and not collected since the GC assumes it doesn't need to collect yet.

Is there any way to make the GC more aggressive, or tell it what the max memory in the environment is?