Support for LPAC on Mobile

Development Platform & Builds Mobile
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1

Is there any planned support for Low Priority Asychronous Compute (LPAC)? In particular this requires the VK_KHR_global_priority extension. This could be very beneficial to mobile chipsets, where we could offload less latency sensitive work to LPAC.

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2

Hi Barnaby,

Async Compute for Vulkan based Android devices is supported as of UE 5.7.2 but hidden behind the r.Vulkan.AllowAsyncCompute CVar. It should be enabled by default in UE 5.8.

Best regards.

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3

Hi Barnaby,

Apologies, I jumped too quick on that as I had noticed your posted listed 5.6 as the referenced UE version. Unfortunately, LPAC/VK_KHR_global_priority isn’t on the current roadmap. However, I’d be happy to communicate any compelling use cases for LPAC specifically back to the development team to have its implementation be considered.

Best regards.

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4

Thanks Barnaby, I’ll pass this on and report back if we get a roadmap item for this. I wouldn’t think the work itself to support LPAC would be overly significant. Keep you posted.

Best regards.

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5

Hi Barnaby,

This will be taken into consideration, particularly for compute work that may span beyond frame boundaries, however, there is no immediate plan to take on this work. It has been generally observed that current mobile chipsets (with the exception of perhaps the AMD based Xclipse) do not show great prowess in their baseline handling of async compute yet.

Best regards

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6

Hi Stéphane, can you confirm if that supports LPAC/VK_KHR_global_priority? As that is in particular what we require rather than just async compute.

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7

Thank you. Our interest is in using LPAC to support background character animation where latency is less sensitive. We would like to offload skinning compute work for those characters to avoid it being performed either using Vertex Animation Textures or with Skin Cache. This would enable us to have much larger crowds on mobile chipsets. We are also interested in using LPAC for VFX and set pieces too.

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