Question Expensive RenderLoop.Prepare issue fix backport to 2021.3 LTS

Hi,

We're currently looking into porting our project over from the built in rendering pipeline to HDRP on the 2021.3 LTS using HDRP version 12.1.6. However, one thing we've noticed during our R&D stress tests for HDRP is lengthy RenderLoop.Prepare calls in jobs, stalling the main thread during the DeferredDepthPrepass.



We've found the issue reported and subsequently solved in 13.1.1 here:
https://issuetracker.unity3d.com/issues/hdrp-renderloop-dot-prepare-takes-up-a-lot-of-cpu

This prompted us to do some comparison tests between the following unity versions and HDRP versions: 2021.3.3f1 (12.1.6), 2020.3.16f1 (10.6), and 2022.1.4f1 (13.1.8). These were our frame time results using the exact same project and scene ported to the 3 different versions:

- 2021.3.3f1 (12.1.6) ~ 56 ms
- 2020.3.16f1 (10.6) ~ 48 ms
- 2022.1.4f1 (13.1.8) ~ 40 ms

As reported, the regression has seemingly been fixed in 13.1.1+ and the RenderLoop.Prepare passes were significantly smaller. However, ideally we would prefer to port to the 2021.3 LTS which only supports the 12.0 major version of HDRP.

Are there plans to have this fix backported to the 2021.3 LTS? If so, how soon can we expect then and if not, is there a some sort of mitigation strategy to avoid these lengthy calls?

Thanks,
Alex