Question Shaders gone from 0.6MB in 2019.4.9 to 350MB in 2020.3.12

Hi

We've recently upgraded a project from Unity 2019.4.9 to 2020.3.12, for a future patch.

After the upgrade, our Windows builds of the game have gone from dedicating 0.6MB of memory to "Shader", to 350MB. In other platforms we've seen it go from 0.6Mb to 540MB.
This is causing the game to crash on consoles, on which we cannot afford to lose 540MB.

I've tried to disable every shader debug or log feature, but shaders are still taking the same room.
We're using addressables, but so did we on 2019. We've created some new groups for the new builds, but not nearly enough to explain a 1000x increament in shader memory usage. No matter how many repeated shaders we have, there's no way we could have gone from 0.6Mb to 350MB, to say nothing of 540MB.
Still, to verify that was not the problem, I've packed almost all shaders in our game into the addressables' Default group. But it's changed nothing. So it does not seem to be a matter of shaders being replicated hundreds or thousands of times.

To make sure it's not something we're doing wrong, I've created a new project with just URP imported, and generated a development build for both PC and the console. In both builds, the URP sample scene uses 23MB for shaders alone, with barely anything in there. That's a lot more than the 0.6MB Unity 2019 used for our whole game.

Can someone at Unity give some insight into what's going on here? I think I'll submit a bug report, once I run some more tests.

2019.4:


2020.3:


2020.3 detail of shaders:

On the console build, SpeedTree goes from the 33Mb in here to 98MB, and Lit from 73MB to 90MB.

 

I don't think that's the case, since there's no "ShaderLab" memory block taking those 540MB on the console's 2019 build, nor 350MB on the 2019 PC build. The 2020 builds are clearly using extra memory, according to the memory captures from Memory Profiler.

Plus, I can't see how compiled shaders would ever use more memory than all the meshes and textures in the scene.

 

My question is, has this changed so much between 2019 and 2020 for it to make a difference of 2 orders of magnitude? Has URP added thousands of variants to Lit and the SpeedTree shaders?
Because I don't think that's the case. It looks more like Unity is keeping lots of debug info on every shader, or keeping everything uncompressed in memory all the time, or something in that vein.

On the console in question, our 2019 builds started gameplay with around 600MB of available memory, and 2020 builds start with less than 200MB, so something is off. And that's memory as reported by the console itself, not Unity's memory profiler.

 

Looks like typical define hell. Did you upgrade URP to newer version too?

 

Yes, we've upgraded from
"com.unity.render-pipelines.universal": "7.3.1"
to
"com.unity.render-pipelines.universal": "10.5.0"

So do you think something is greedily adding each and every shader variant into the build?
I finally have the time to check what's going on in more detail, so I'm going to generate a new build and check the log thoroughly.