b10840

CUDA: branchless Q4_K/Q5_K unpack to speed up mmvq, L2 prefetch on DGX Spark (#26705)

• Update Q4_K and Q5_K to use branchless computation, which stops the scale unpack being re-executed for every column in mmvq, improving perf at batch sizes > 1

• Gating the change off from DGX Spark due to no gain

• Adding prefetch gated to Spark, making branchless change in Q4_K and Q5_K general and modifying switch points based on latest perf data

• Guard the mmvq L2 prefetch against MUSA as well as HIP

• Define the mmvq L2 prefetch only under the Spark guard

• Update switch point for Q4_K to accommodate more models

• Remove stale comments

• Add block_size to ggml_cuda_type_traits and create a separate mmvq_should_prefetch function

• Rename block_size to bs for cleaner indentation

• Fix build error on non-Spark CUDA arch with appropriate conditional around new function added

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Co-authored-by: praneshgo 227579474+praneshgo@users.noreply.github.com

Website:

• https://llama.app

Attestations:

• https://github.com/ggml-org/llama.cpp/attestations/45763558

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