iOS large CPU spike/hang intermittently around AutoReadLockT

On a couple devices (iPad Air 1 & 2) we are seeing problems with the CPU spiking and locking the main thread. This was tested under Unity 2018.1.8f1.

Using Xcode instruments we have noticed that when the CPU spikes on the main thread there is also another thread showing the exact same spike and it appears to be a graphics worker thread with the entry function being GfxDeviceWorker::RunGfxDeviceWorker(void*).

Both threads effectively stall on "AutoReadLockT" for varying amounts of time between 20-60 seconds but the issue does eventually resolve itself. The stack trace varies slightly when we can reproduce the issue, but the stack trace is always the same at the final few lines:

AutoReadLockT

GetAllocationRoot

MemoryProfiler::UnregisterAllocation

MemoryProfiler::UnregisterAllocation

MemoryManager::RegisterDeallocation

MemoryManager::Deallocate

deallocate

One of the places this happens on the main thread is from AnimatorController::MainThreadCleanup which calls AnimatorController::ClearAsset which eventually hits the stall on AutoReadLockT.

We haven't been able to narrow down exactly what is causing this. Unfortunately it seems to be just playing the game for ~30 minutes and eventually it will happen. Has anyone run into something similar or have any troubleshooting suggestions?

 

I have also encountered the very same problem.
this problem seems to occur only in Unity 2018(not in Unity 2017).
It tends to be reproduced if I repeat large amount of generation and destruction of assets.
In my situation, this issue will not occur if I turn off the "Development Build" flag.
This may be a bug which happened from Unity 2018...

 

Hi, the very same symptoms we see in our project. Is there a ticket we can follow to get the status of the issue? We're now on 2018.1.6f1.

 

Hi! Does this mean Unity 2018.2 will get a fix for this eventually?

We have been having this issue when calling Resources.UnloadUnusedAssets. The game freezes to AutoReadLockT, with both main thread and GfxDeviceWorker having high CPU usage. It will stay like that for several minutes. Tested on Unity 2018.2.6 and 2018.2.9, different Apple devices and iOS versions.

Haven't tried non-development build yet, but I will do that next.

EDIT: Here's a trace from instruments:

 

@Aurimas-Cernius Any news? Is there a version with this thing being fixed?