Select batched memcpy flags by copy size - #1152
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Signed-off-by: Bradley Dice <bdice@bradleydice.com>
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Description
This addresses a performance issue documented in NVIDIA/cudf#23674.
Use
cudaMemcpyFlagPreferOverlapWithComputefor acudaMemcpyBatchAsyncbatch only when every copy is 128 KiB or less. If any copy is larger, usecudaMemcpyFlagDefaultfor the entire batch. The choice of 128 KiB was determined by benchmarking on several devices (GB300, GB10, RTX PRO A6000) and minimizing the time cost modeled with latency and bandwidth.Checklist