Knowledge Base: Tech Note: Fix for PSO Management Issue on Nvidia Hardware in Unreal Engine 5.5

General Tutorial & Course Discussions
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A critical stability issue has been identified in Unreal Engine versions 5.5 and above, affecting projects running on Nvidia hardware, particularly with recent driver versions. This post describes a way to integrate a fix for this issue.

https://dev.epicgames.com/community/learning/knowledge-base/DBOL/tech-note-fix-for-pso-management-issue-on-nvidia-hardware-in-unreal-engine-5-5

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When does this get taken updated with vendors like Wildcard and nvidia?
The Game ARK ASa is having major issues with this due to the pipelines.

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In addition to the CL mentioned in the Tech Note above, we also recommend integrating the following change to defer the deletion of the PSOs and avoid potential hitching - in some cases over 100ms.

CL#43368107 Defer deletion of ID3D12PipelineState objects.

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Hi,

For stability reasons, retaining too many PSO objects at the driver level may lead to instability issues. However, the downside is that once the low-level D3D12 PSOs are released, encountering the same PSOs again later may require recreating them, which can cause runtime hitches.

One possible mitigation we are considering is enabling:

D3D12.PSO.DriverOptimizedDiskCache=1

Our idea is to keep:

D3D12.PSO.KeepUsedPSOsInLowLevelCache=0

This would still allow live low-level PSO objects to be released, while using the driver-optimized disk cache / ID3D12PipelineLibrary path to reduce the cost of recreating those PSOs later.

We have a few questions:

When KeepUsedPSOsInLowLevelCache is disabled, would enabling D3D12.PSO.DriverOptimizedDiskCache be considered a safe way to reduce PSO recreation hitches while also avoiding this driver instability issue? I am concerned that ID3D12PipelineLibrary may internally retain some form of driver-level PSO data, such that even after the actual ID3D12PipelineState objects have been released, it could still contribute to the same NVIDIA PSO management / stability issue.

If DriverOptimizedDiskCache is not recommended in this scenario, is there another recommended approach that can both reduce hitches caused by PSO recreation and avoid long-term accumulation of live D3D12 PSO objects?

Thank you very much.