Bug (Case 1291333) Library ShaderCache grows in size over-time until AssetDatabase.Hotreload is incredib

I'm getting no response from QA on this issue. Hopefully someone from Unity can take a look.

Library ShaderCache grows in size over-time until AssetDatabase.Hotreload is incredibly slow from searching the cache. This reproducibly destroys the performance of most import actions and flags a question as to why shaders are being touched when importing nonshader assets.

 

(Case 1291333) is the report for this issue. I've attached my shader cache dir, basically, you can see in the profiler when importing a shader that there is an incredibly slow set of calls to Shader.EditorLoadVariantFromCache under AssetDatabase.V2.Hotreload when the cache folder is present. Deleting the cache means the hotreload occurs almost instantly. This manifests as a long freeze of the editor when saving/importing a shader that does not occur when the cache is gone. In my case, the cache is a few GB so it could be that it's accumulated more than normally expected.

When using ProcMon I can see that many FileIO operations occur on the ShaderCache Dir when importing scripts. This could be valid as maybe they all need to be reloaded after a Domain Reload?

Attached are two screenshots of the profiler.

 

This is a gDrive link to the cache if needed: https://drive.google.com/file/d/1LwgHah0g1VrRmZ7qjVlJ7-XO7N0iX5zU/view

 

Some of the members of our team are getting freezes lasting over 30 seconds when saving trivial changes to shader files. These extreme cases are also resolved by deleting the cache

 

Another note is that originally this was an ADBv1 project so there could be an upgrade related issue here?

 

I've still not received any update from QA on the ticket, is there any additional info they might need to look into this?

(Case 1291333)
https://fogbugz.unity3d.com/default.asp?1291333_8gb8hestlf88sme1

 

So there is a missing component to this. AmplifyShaderEditor kicks off the AssetDatabase.Hotreload call, so the underlying issue in within unity but is only triggered by ASE. I'll add this to the ticket and give QA the ASE package in a new proj but it does make me a bit worried that this issue might fall through the cracks between Unity and ASE

 

You can see in the screenshots further up in the thread that AssetDatabase.V2.Hotreload has Shader.EditorLoadVariantFromCache as a child. EditorLoadVariantFromCache does a large amount of File.Open when the shader cache is large.

Deleting the shader cache will reduce the overhead of EditorLoadVariantFromCache as there are many fewer File.Open's.

Is it possible that you're looking at more recent implementations that have removed the EditorLoadVariantFromCache call from Hotreload?

 

No its the same runtime case. We dont change anything to do with the shaders or rendering themselves. I suspect its opening 15k files because its traversing the entire directory. Each previous iteration of the shader is left in the directory when the shader is recompiled, so the majority of those are likely just dead old versions.

 

I think he already answered it:

 

Yes it is true that the overhead is reduced but the actual variants in use is identical

 

Sure thing, I'll link this thread in too

 

Probably similar case: unity started to hang everywhere (enter playmode, exit, recompile c# scripts, recompile shaders) without any recent import of assets.
Found with procmon the most time unity spent on Library/ShaderCache (~40k files), i clean it up. Layouts are crashed one time, but everything started to work w/o any delays

 

Had my shader cache swell to over 8gb in a project just increasing in size with every build for an IOS app!

It seems to be connected to a massive hang when opening the shader dropdown on a material to change shader, can take up to 2 mins to open that dropdown sometimes.

Using Unity 2020.3.0f1

 

Great I'll bump to that then cheers

 

2021.3.0f1 and the issue still appears BUT i fixed it by moving the project to my HDD (instead of SSD)

Hope it helps anybody