iOS memory usage increasing, can't find the culprit

Question

I'm attempting to download a large number of images using AFNetworking 2.5 and stream them to disk. According to the memory monitor in Xcode, this is causing unbounded memory growth (and eventually memory warnings and force quits) - but profiling the memory usage using the allocations instrument shows the memory usage to be stable.

I'd like to think Xcode is just wrong here, but then why would my app be getting killed by iOS?

Instruments shows this - the peaks are Core Data queries, then the rest is the images downloading - peaks at about 9.5MB, the rest sits at about 8.5MB

I've also tried Heapshot Analysis - which shows a tiny bit of growth but nowhere near the amount reported by Xcode

Xcode's memory monitor shows this - growing by multiple MB per iteration.

Is there any way to get Instruments to show me whatever Xcode is seeing? Or is there a better instrument to use to find out where all this memory is going?

Thanks!

Answer 1

According to the memory monitor in Xcode, this is causing unbounded memory growth (and eventually memory warnings and force quits) - but profiling the memory usage using the allocations instrument shows the memory usage to be stable.

Believe Instruments and the Allocations information - not the memory monitor in Xcode. The memory monitor graph is completely irrelevant. Ignore it.

This is not because the memory monitor in Xcode is useless or wrong. It is because memory management is completely different for a debug build than for a release build (Instruments uses a release build). This is especially true in Swift (you don't say whether you're using Swift).

Observe memory usage only on the device and only in a release build. Otherwise, you'll be completely misled.