Draft: Megatron-FSDP and PP compatible support #2302
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1. Upgrade DeviceMesh initialization for M-Core to support heterogeneous parallelism. 2. Fix an issue where parameters remain as dist-param during forward execution in specific cases.
2. Fix grad reduce hang issue
2. Hide pipeline schedule's deallocate_output_tensor activation reference check for Megatron-FSDP compatibility. Deallocation is usually harmless for activations with views.
megatron/core/distributed/fsdp/src/megatron_fsdp/benchmark_utils.py
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megatron/core/distributed/fsdp/src/megatron_fsdp/benchmark_utils.py
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| else: | ||
| dp_size = dist.get_world_size(dp_cp_group) | ||
| dp_cp_tp_ranks = [None for _ in range(dp_size)] | ||
| dist.all_gather_object(dp_cp_tp_ranks, tp_ranks, group=dp_cp_group) |
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Hmm, because we use all_gather_objects, we cannot make these two calls async... :(
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Do you mean it can be optimized into an all_gather operation?
| help='If set, enable full sharding in megatron-fsdp Hybrid Sharded Data Parallel (HSDP) mode.') | ||
| group.add_argument('--num-distributed-optimizer-instances', type=int, default=1, | ||
| help='Number of Distributed Optimizer copies across Data Parallel domain.') | ||
| group.add_argument('--no-mfsdp-comm', action='store_true', |
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Consider using argparse.BooleanOptionalAction so a use can explicitly opt in too
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argparse.BooleanOptionalAction requires Python 3.9, so I think it's best to use it with caution.
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@shjwudp What's the minimum supported Python version for Megatron as of now? 3.9 is way past EOL?
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Will this support VPP and help making FSDP more viable for training MOE models? |
… TP-duplicated mesh 2. Minor code polish 3. Code formatting
@Skylion007 There are performance concerns with combining VPP and FSDP (VPP makes FSDP prefetching difficult), so I am not sure this will be beneficial for MoE training. However, I will try to make this PR support VPP as well so that we have more options. |
Ah what I really want is to support A2A overlap with FSDP which requires VPP. |
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