[Task][Megatron] 3.4: Performance benchmark suite

[lvyufeng]

Parent Issue

Part of #206 — Megatron Roadmap, Phase 3 (Megatron Core Execution MVP): Task 3.4

Description

Benchmark step time, communication overlap, and scalability on NPU.

Requirements

• Per-step time breakdown (compute, communication, overlap)
• Scaling efficiency across NPU counts (2, 4, 8)
• Communication-computation overlap measurement
• Memory usage per rank
• Comparison against torch_npu + Megatron baseline
• Reproducible benchmark scripts

Blocked By

• [Task][Megatron] 3.1: NPU-first end-to-end Megatron training smoke test #259 (E2E smoke test)

Blocks

• Performance optimization roadmap