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h-guo18 46eddab877 [Feat]: Specdec Streaming: RDMA + Multinode (#1611)
### What does this PR do?

Type of change: New feature

Multi-node **streaming** training for speculative decoding (EAGLE3 /
DFlash):
a live `vllm serve` captures the target model's hidden states and moves
them
straight to the trainer over **NIXL RDMA** — no disk round-trip. The
streaming
dataset is map-style — each rank fetches only its own
`DistributedSampler` shard
(concurrency from `dataloader_num_workers`), round-robins across
multiple serve
replicas (`server_urls`), and scales to multi-node DDP. Serve-side
tensor
parallelism (TP>1) is supported: hidden states are replicated across TP
ranks, so
rank 0 alone owns the pool + transfer.

### How

- `RdmaHiddenStatesConnector` — out-of-tree vLLM connector (no vLLM
source edits):
one pre-registered pinned NIXL pool per serve, a ring slot per request,
and a
small HTTP sidecar serving transfer metadata. The trainer RDMA-READs the
slot
  into a per-worker buffer. RDMA is the **only** transport (the earlier
  disk/safetensors path is removed).
- Map-style dataset + multi-node accelerate launch (`--machine_rank`,
optional
  Slurm `--segment` to keep nodes in one NVLink domain).

### Usage

```yaml
data:
  mode: streaming
  streaming_server_url: "http://node0:8000,http://node1:8000"  # round-robin
```

### Validation (Qwen3-8B, oci-nrt H100)
sandbox CI:
https://gitlab-master.nvidia.com/omniml/integration/nmm-sandbox/-/jobs/337489812

**1. End-to-end convergence — EAGLE3 & DFlash, 5000 steps.** Both
algorithms
converge and export a deployable draft; the DFlash drafts also serve
under vLLM
speculative decoding (8/8 smoke prompts pass).

| algorithm | topology (nodes) | train loss (step 0 → 5000) | vLLM draft
acc-len |
|---|---|---|---|
| EAGLE3 | 2 serve TP=2 + 2 trainer DDP (4) | 37.1 → 8.20 | — |
| DFlash | 1 serve TP=1 + 1 trainer (2)      | 11.7 → 5.56 | 1.11 |
| DFlash | 2 serve TP=2 + 2 trainer DDP (4)  | 10.9 → 5.26 | 1.19 |

<!-- Drag these PNGs in here (GitHub turns them into asset URLs):
eagle3_streaming_loss.png, dflash_streaming_loss_singlenode.png,
dflash_streaming_loss_multinode.png -->

**2. Scalability — 1 → 12 nodes (EAGLE3, 200 steps).** Throughput scales
~23× across the
sweep below. The step-time growth is cross-node DDP all-reduce, not the
streaming path —
RDMA (~0.33 ms/req @ 2 MB, ~47 GB/s host-pinned READ) is never the
bottleneck. Scale
serve + trainer nodes together for near-linear speedup.

| serve / trainer | nodes | step time | samples / step | samples / sec
(global) | acc @ step 200 |
|---|---|---|---|---|---|
| 1 serve / 1 rank (co-located, 1 node 2 GPU) | 1 | 0.23 s | 1 | 4.4 |
[0.141, 0.094, 0.072] |
| 1 serve / 1 rank (cross-node) | 2 | 0.23 s | 1 | 4.3 | [0.137, 0.105,
0.074] |
| 2 serve / 8 ranks | 3 | 0.26 s | 8 | 31.1 | [0.215, 0.126, 0.097] |
| 4 serve / 16 ranks (2 trainer nodes) | 6 | 0.28 s | 16 | 56.5 |
[0.217, 0.148, 0.110] |
| 8 serve / 32 ranks (4 trainer nodes) | 12 | 0.31 s | 32 | 101.9 |
[0.235, 0.165, 0.137] |

**3. Serve-side TP correctness.** TP=1 vs TP=2 draft top-1 accuracy
track
step-for-step (hidden states are replicated across TP ranks).

<img width="910" height="546" alt="serve-tp-acc"
src="https://github.com/user-attachments/assets/73df9214-7ff0-4ab4-bf2f-95842b12cd5f"
/>

### Before your PR is "*Ready for review*"

- Backward compatible?: ❌ — streaming is now RDMA-only; `server_url` →
`server_urls`;
the disk transport (`HS_TRANSPORT`, `streaming_shared_storage_path`) is
removed.
- New tests?: ✅
`tests/unit/torch/speculative/plugins/test_hf_streaming_dataset.py`
  (map-style dataset + mocked RDMA fetch).
- Updated Changelog?: ❌
- Claude approval?: ❌

---------

Signed-off-by: h-guo18 <67671475+h-guo18@users.noreply.github.com>
2026-06-10 18:35:02 -07:00

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#!/bin/bash
# SPDX-FileCopyrightText: Copyright (c) 2024 NVIDIA CORPORATION & AFFILIATES. All rights reserved.
# SPDX-License-Identifier: Apache-2.0
#
# Licensed under the Apache License, Version 2.0 (the "License");
# you may not use this file except in compliance with the License.
# You may obtain a copy of the License at
#
# http://www.apache.org/licenses/LICENSE-2.0
#
# Unless required by applicable law or agreed to in writing, software
# distributed under the License is distributed on an "AS IS" BASIS,
# WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
# See the License for the specific language governing permissions and
# limitations under the License.
# Usage:
# Single GPU: ./launch_train.sh --config ../../modelopt_recipes/general/speculative_decoding/eagle3.yaml model.model_name_or_path=xxx
# Multi-node: ./launch_train.sh --config ../../modelopt_recipes/general/speculative_decoding/eagle3.yaml --num_nodes 2 --head_node_ip <IP>
# With overrides: ./launch_train.sh --config my.yaml model.model_name_or_path=xxx training.output_dir=yyy
#
# Extra key=value args are forwarded as OmegaConf dotlist overrides to main.py; all
# training config lives in the YAML. mixed_precision is fixed to bf16.
set -eo pipefail
SCRIPT_DIR="$(dirname "$(readlink -f "$0")")"
CONFIG_FILE=""
NUM_NODES=1
HEAD_NODE_IP=""
MACHINE_RANK=""
EXTRA_ARGS=()
while [ $# -gt 0 ]; do
case "$1" in
--config*) if [[ "$1" != *=* ]]; then shift; fi; CONFIG_FILE="${1#*=}" ;;
--num_nodes*) if [[ "$1" != *=* ]]; then shift; fi; NUM_NODES="${1#*=}" ;;
--head_node_ip*) if [[ "$1" != *=* ]]; then shift; fi; HEAD_NODE_IP="${1#*=}" ;;
--machine_rank*) if [[ "$1" != *=* ]]; then shift; fi; MACHINE_RANK="${1#*=}" ;;
*) EXTRA_ARGS+=("$1") ;;
esac
shift
done
if [ -z "$CONFIG_FILE" ]; then
>&2 echo "Usage: ./launch_train.sh --config <yaml_file> [--num_nodes N] [--head_node_ip IP] [key=value ...]"
exit 1
fi
if [[ "$NUM_NODES" != "1" ]]; then
GPU_PER_NODE=${GPU_PER_NODE:-$(nvidia-smi --query-gpu=name --format=csv,noheader | wc -l)}
TOTAL_GPU=$((NUM_NODES * GPU_PER_NODE))
echo "Total GPUs: $TOTAL_GPU (NUM_NODES: $NUM_NODES, GPU_PER_NODE: $GPU_PER_NODE)"
else
TOTAL_GPU=$(python3 -c "import torch; print(torch.cuda.device_count())")
echo "Total GPUs: $TOTAL_GPU (single node)"
fi
MULTI_NODE_ARGS=()
if [[ "$NUM_NODES" != "1" ]]; then
# --multi_gpu is required even at 1 GPU/node, else accelerate won't form the DDP group.
# machine_rank defaults to $SLURM_PROCID; override --machine_rank if node 0 isn't a trainer.
MULTI_NODE_ARGS=(
--multi_gpu
--num_processes "$TOTAL_GPU"
--num_machines "$NUM_NODES"
--machine_rank "${MACHINE_RANK:-$SLURM_PROCID}"
--main_process_ip "$HEAD_NODE_IP"
--main_process_port 29500
)
fi
export TOKENIZERS_PARALLELISM=False
# argv array, not `sh -c` (which would word-split overrides and run embedded substitutions).
CMD=(accelerate launch --mixed_precision bf16
"${MULTI_NODE_ARGS[@]}"
"${SCRIPT_DIR}/main.py" --config "$CONFIG_FILE" "${EXTRA_ARGS[@]}")
set -x
start_time=$(date +%s)
"${CMD[@]}"
echo "Total time: $(( $(date +%s) - $start_time )) seconds"