400ms lag spikes in the profiler due to HDRenderPipleline camera render

[joe1275]

I just switched over my game from UDP to HDRP, and it seems the camera’s HDRP script is causing lag spikes. When I remove the MainCamera and play the game, the lag spikes go away even when I move around in the world. (obviously cant see anything though). Each spike is a different call in the function that I selected there.
Any idea what could be causing this?

UPDATE 1

All of the lag spikes are under that first one InI_ExecuteRenderGraph, but each time they end with a different function call, the first spike is waiting on

1. RenderGraphResourceRegistry.GetTextureResource()
2. is Stack1.get_Count() under RenderGraphObjectPool.GetTempArray()
3. is ResourceHandle.get_iType()
4. is Object.IsNativeObjectAlive()

and so on for each spike.

Its never the same thing. Each one takes 400ms and causes a lag spike, not sure how they could be connected though

[andrew-lukasik]

You may want to look into this InI_ExecuteRenderGraph marker as it seems to be the one that is blocking the main thread here.

→ https://forum.unity.com/threads/guide-to-unity-profiler-hdrp-version-and-how-to-read-gpu-cpu-profiler-data.1408699/

@quote from linked thread

1. InI_ExecuteRenderGraph": This is where you will find most rendering metrics, inside this one.
2. “InI_RecordRenderGraph”: HDRP uses a rendergraph, this simplifies some graphic wizardy and can lead to reduced VRAM usage, there’s little to nothing you can do about this one to reduce it’s costs. Possibly enabling “Dynamic Render Pass Culling” in HDRP global settings can slightly improve it’s performance.
3. “PrepareLightsForGPU”: This does some graphics wizardy for realtime/mixed lights in HDRP. The more lights you have, the more this will cost. Since 2022.1 this got a big performance improvements and HDRP in the background uses jobs and burst to speed it up.
4. “Shadows.PrepareDrawShadows”: This is similar to PrepareLightsForGPU, but for shadows. The more realtime shadows you have, the more it will cost. This has been optimized in 2023.1, and will utilize burst/jobs for better CPU performance.

The following are metrics inside “ExecuteRenderGraph”:
5 “RenderShadowMaps”: This is CPU overhead for realtime shadows. The more shadow caster objects you have, and the more lights that cast shadows, the more expensive it will be.
6. “GBuffer”: overhead, same as GPU Gbuffer, has to do with number of objects, and polygon count. Make sure you’re utilizing SRP batcher well to reduce it’s cost.
7. “DeferredDepthPrepass”: Does a depth prepass for the deferred renderer.
8. “Deferred Lighting”: This cost comes from realtime lights, and their range.
9. “ObjectsMotionVector”: This cost comes from objects with motion vector mode set to Object mode. The more objects you have set to objects mode, the more expensive. Things that need object motion vectors are animated meshes, such as grass. (Motion vectors help TAA/Motion blur to give better results).
10. “ForwardTransparent”: Transparent objects can’t be rendered in deferred mode, so even if you’re using deferred mode, HDRP will render transparent objects in forward mode.
11. “PostProcessing”: Cost of post processing overhead.
11. “DBufferRender”: Decal cost (when using deferred).