Loading.IDRemapping AssetBundles

Does anyone know what Loading.IDRemapping actually does?

I’ve been profiling my game and Loading.IDRemapping is getting called 50k+ times even though I’m only trying to load a sprite from a spritesheet. This happens even after the first time it’s been called (so the sprite should have been loaded?).

It seems to also be calling IDRemapping on the same asset multiple times. I don’t think I have 50k+ assets.

Google searching Loading.IDRemapping returns nothing relevant, but from this screenshot it seems to stem from AssetBundles

I found this problem with big asset bundles (>1GB uncompressed) too. Loading.IDRemapping is called over 1 million times in a single call to AssetBundle.LoadAsset. In mobile phone with Qualcomm 801, it cost 10 seconds to load the prefab. I reproduced the bug in Unity 5.3.6f1 and 5.5.0f3. Resources.Load seems OK with the prefab.

As this article suggests, I should use asset bundle instead of Resources mechanism. But asset bundle cannot offer feasible performance as Resources.Load.