Question Tracking down "Unknown" memory allocation leak

The image below pretty much says it. I've got a pretty bad memory leak in my game right now and I'm not sure what types of things are tracked under the 'Unknown' memory category. Any pointers would be helpful.

This leak appears to happen in both the editor and standalone builds. I'm using 2022.2.8

 

The memory profiler might give you more information
https://docs.unity3d.com/Packages/com.unity.memoryprofiler@1.0/manual/index.html

 

That's a screenshot from the memory profiler. Specifically the diffing view between two snapshots. (A) was taken not long after (B). The only appreciable difference in memory in the 'Unknown' block

 

My bad. I thought, it was a screenshot from the memory profiler module, which has similar stats.

Can't you just look at the details then? Or does it not show you because it is non-managed memory?

 

Yeah there's nothing there because of the type of memory it is.

Something I figured out today is that this isn't actually a leak. I wrote a very simple cross fade shader via a URP render feature (it's literally)

Code (CSharp):

1.             half4 frag(Varyings IN) : SV_Target
2.             {
3.                 return _TargetWeight * tex2D(_PrimaryTex, IN.texcoord)
4.                     + (1. - _TargetWeight) * tex2D(_SecondaryTex, IN.texcoord);
5.             }

.. and what's happening is that when I turn off vsync and when this shader is running, the game's framerate becomes erratic like, between 2 FPS and 200 and watching the process in task manager I see the executable's memory footprint shoot up from 500 mb to upwards 6 gb, and then rapidly come back down afterward.

The thing that has me flummoxed now is why this only seems to happen when the game is running at a high frame-rate and where the heck all this unmanaged memory is coming from? It's somewhat difficult to reproduce in-editor and debug builds but is pretty consistent in an optimized release one.

 

It's certainly not the shader itself but hard to tell whether it is a CPU or GPU problem.
I would profile the standalone build with NSight Systems and optionally with NSight graphics.
Maybe somebody knows also a good memory profiler for native memory.

 

Interesting, I hadn't heard of that tool. I'll give it a go tonight. I also need to carefully review how the render feature I wrote gets setup on a per-frame basis. It's pretty simple but I didn't put a ton of care into it.

 

I'm just beginning to try and parse this data, but thought I'd share what the app looks like in one of the simplest scenes. pretty much static geometry, not scripts not really running any per. frame logic.



Why is every other frame long (~2ms / ~10ms)

 

Good question, no idea. Hope you'll find something in there that will give you a clue.

 

Things look more consistent with maxQueuedFrames set to 3 instead of 2; I'm guessing with 2 swapchain buffers the CPU is getting blocked by the GPU?

 

Anyway, the important thing is the repro case. I actually got it captured

 

The HW Scheduler - Copy load wasn't there in the first picture, so with all the information you have given us so far, my guess is that you are creating a new texture or rendertexture every frame that you are not releasing. That will eventually force the GPU to move stuff over from VRAM to RAM.

 

The game runs just fine at 60 fps with vsync on for extended periods of time. I ran it for a couple hours last night.

If I flip vsync off, it will often repro within a couple seconds. There's also been a pattern where this will happen and then the frame rate recovers. If I watch system memory in the task manager for the game process it'll go from 500mb, spike upwards to 6gb but then come back down again.

I agree there's obviously something going on with memory here, it does feel like a thrashing problem but I don't think I'm leaking render textures. I'm going to dig into this capture a bit more but I will look around for things like render texture abuse

 

It is possible that the garbage collector can't keep up with the garbage created if the frame rate is very high but obviously, I'm just poking around in the dark.

 

Yeah, the stabs are helpful so I appreciate it. I think this type of memory is also captured in the unity memory profile

 

Hey dyamanoha_, have you found the cause of your issue?