Skip size calculation during async copy wait=True

[rupengliu-meta]

Thanks to @bythew3i (Jevin) for providing the insight for the optimization. This is to skip size computation during DMA wait.

I have ran both kernel's test and brought up e2e vllm server to test, will provide perf improvement numbers

Signed-off-by: Rupeng Liu rupengliu@meta.com

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[kyuyeunk]

Just to double check, is it using same optimization as this PR? #718

Maybe we should wait until response from @lsy323 and only merge it if there is no response?

I have ran both kernel's test and brought up e2e vllm server to test, will provide perf improvement numbers

Can you provide more concrete performance number in the description?

Also, please fix pre-commit failures.