Addressable System does not release memory after assets completely released

Unity Engine
1

Hello,
I’ve been tasked with improving memory usage and it seems that Addressable Asset System is the best for the purpose. I came up with a simple Android app to get familiar with Addressable and to see how it effects memory. Inside the app, I will load a sequence of assets (sprite atlases, sizes vary from 1MB to 16MB) and then release them (in reversed order). There are 11 loads and 11 releases. At each load/release, I check Android Studio’s Memory Profiler and record memory usage into a spreadsheet for comparison.

What I naively expected to see in Memory Profiler

  • When an atlas is loaded, the memory would increase the exact amount as the atlas size
  • When an atlas is released, the memory would decrease the same amount

The first thing I noted in Memory Profiler was that Graphics memory was the only that varied during loading/releasing which made perfect sense (Java and Code memory did vary but in a random way, so I think they can be ignored)

I have tested with 8 devices and the results are interesting

  • Group 1 (Oppo, Vsmart, Samsung, Huawei, LG): the memory changes seem intuitively, it increase with load, and decrease with release. But the amount of increase/decrease is not always the same as the size of the atlas being loaded/released
  • Group 2 (Xiaomi Note 5, Xiaomi Note 7 and Google Pixel 4XL): memory increases to its peak after a few loads, and remain unchanged for subsequent loads/release

(You can see this in the attached file)

And this held true for all devices: memory after releasing all atlases is bigger than the memory at start (no atlas loaded), it’s about 32M more (total atlases are 70MB)

So here are the questions :

  • Does Addressable not work in Group 2, since memory never gets released ?
  • Why is memory after all atlases released even bigger than when start ?
  • Why does memory behave so differently between those groups ?

Any help would be appreciated !

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2

I would check memory usage with Memory Profiler package or built-in in Unity Profiler memory module.
From the screenshots I can see that Group2 (mostly) has memory usage <75MB. This could be the case of memory pools fragmentation which settle game memory usage to the certain amount of allocated memory.

Unity allocates memory from a system in larger chunks (1-4-16MB) and releases it in chunks too. If a chunk has an active allocation from some system or any persistent asset, it stays in memory - it is technically a memory reservation Unity uses for later loads.

My feeling is that the picture your see on different devices is a combination of texture format and the pool memory system Unity uses - more likely on some phones the textures are unpacked causing higher memory mark and then released settling the memory usage at pools reservation level 75-100MB. However LG phone stands out with 35MB…

3

For future people I’ll post this:

  • check your AddressableGroupSettings.BundleMode should be ‘Pack Separately’, to unload AssetBundles independently from each other
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