Question about speeding up PSO pre-warm

Mobile game now requires massive amount of PSO to pre-warm to prevent CPU hitching during game play.

Even after removing redundant permutations, it still requires minutes to warmup the cache on mainstream devices.

Luckily, UE5 gives us a solution, we can compile PSO in async style in different android services(A service is a long running background task in Android, kind like a separate process.) to speed up the process.

https://github.com/EpicGames/UnrealEngine/commit/aa7ba3ecfd05d3d2b9a12c9d2d4131b9d78e3a42

https://github.com/EpicGames/UnrealEngine/commit/bde84ad858735d44180a1c9e1a749a1350a4906f

This works fine in OpenGL RHI, it gives us a 2x compile time boost.

But it's worse in Vulkan RHI. Both approach looks identical, i wonder if there's any restriction in vulkan's driver implementation that limits this use pattern.