[shjwudp]

What does this PR do ?

dev PR: #2627

Add a switch to control whether to prefetch the first parameter group of M-FSDP before the forward loop.

• Prefetching the first parameter group before the forward loop can help launch kernels earlier, help improving throughput.
• Skipping this step ensures compatibility with CUDA Graph capture.

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flowchart LR
    A[Pre-checks] --> B[PR Tests]
    subgraph Code Review/Approval
        C1[Expert Review] --> C2[Final Review]
    end
    B --> C1
    C2 --> D[Merge]

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[shjwudp]

/ok to test 98ad293

[cspades]

Approving to unblock - doesn't need to be added to fully_shard since start_param_sync is not utilized there.

[gautham-kollu]

/ok to test 28a2672

[shjwudp]

/ok to test 5b4204d

[ko3n1g]

🔄 Merge queue validation started!

You can track the progress here: https://github.com/NVIDIA/Megatron-LM/actions/runs/22082721189

[svcnvidia-nemo-ci]

🔄 Merge queue validation started!

You can track the progress here: https://github.com/NVIDIA/Megatron-LM/actions/runs/22155395898

[svcnvidia-nemo-ci]

🔄 Merge queue validation started!

You can track the progress here: https://github.com/NVIDIA/Megatron-LM/actions/runs/22158203441