Bug Server world allocations live too long in 0.50 preview 29

By creating a fresh project and just importing the latest netcode package (0.50.0-preview.29) the leak detection system complains about deleting allocations that are too old.

Code (CSharp):

1. Internal: deleting an allocation that is older than its permitted lifetime of 4 frames (age = 6)
2. UnityEngine.StackTraceUtility:ExtractStackTrace ()
3. Unity.Collections.Memory/Unmanaged/Array:Resize

this happens every frame. Apart from deactivating leak detection, is there currently another workaround?

 

Yes, the current framerate is 72FPS (potentially 90 FPS).

But I could resolve it by enabling VSync in the GameView window. Are currently higher framerates than 60FPS not supported by netcode?

 

I'm seeing a single random leak even with vsync enabled right at the start of the game.

My current setup is there is always a client world even in the menu and when you start game a server world is created.

I think it's the point where I create the server world that it leaks.

I'll do more debugging at some point when it bothers me enough, but I never saw this pre-update.

 

I can confirm. Fresh 2020.3.30 project with the following packages: Entities, Physics, HybridRenderer has no warnings spam, but warnings appear as soon as Netcode package is added

I don't think I was seeing this in previous versions

 

Based off the change log this should actually be fixed

https://docs.unity3d.com/Packages/com.unity.entities@0.50/changelog/CHANGELOG.html

Except looking at the source code this change log is a lie

Code (CSharp):

1.         public EntityCommandBuffer CreateCommandBuffer()
2.         {
3.             var cmds = new EntityCommandBuffer(Allocator.TempJob, -1, PlaybackPolicy.SinglePlayback);
4.             var world = World.Unmanaged;
5.             var state = world.ResolveSystemState(world.ExecutingSystem);
6.             cmds.SystemID = state != null ? state->m_SystemID : 0;
7.             cmds.OriginSystemHandle = state != null ? state->m_Handle : default;
8.  
9.             m_PendingBuffers.Add(cmds);
10.  
11.             return cmds;
12.         }

It's still using TempJob not World.UpdateAllocator.

 

Does this mean that there now is a TempJob-like allocator that we can use which doesn't generate those warnings?

 

The new World.UpdateAllocator is tied to World Update rate not frame rate and resets every 2 frames (because there are 2 of them that alternate.) You don't need to worry about disposing it either.

You can use it like

NativeArray<int> array = CollectionHelper.CreateNativeArray<int, RewindableAllocator>(1234, ref this.World.UpdateAllocator);

 

What is the recommendation/fix here? Is there even a way to wallpaper over this until a pkg fix is released?

 

For anyone looking to fix this in the meantime. You will need to:

- Make com.unity.entities a local package. You can do this by going to the Library/PackageCache/ and copying com.unity.entities@0.50.1-preview.2 to a local path, and then adding a local package in the Package Manager

- In EntityCommandBufferSystem, line 83, change Allocator.TempJob to World.UpdateAllocator.ToAllocator (see below)

Code (CSharp):

1.         public EntityCommandBuffer CreateCommandBuffer()
2.         {
3.             // var cmds = new EntityCommandBuffer(Allocator.TempJob, -1, PlaybackPolicy.SinglePlayback);
4.             var cmds = new EntityCommandBuffer(World.UpdateAllocator.ToAllocator, -1, PlaybackPolicy.SinglePlayback);
5.  
6.             var world = World.Unmanaged;
7.             var state = world.ResolveSystemState(world.ExecutingSystem);
8.             cmds.SystemID = state != null ? state->m_SystemID : 0;
9.             cmds.OriginSystemHandle = state != null ? state->m_Handle : default;
10.  
11.             m_PendingBuffers.Add(cmds);
12.  
13.             return cmds;
14.         }
15.  

 

Is there any docs where I can read about this new allocator?