[Documentation][Configuration] Server args and documentation of PD-Multiplexing. (#11427)

docs/advanced_features/pd_multiplexing.md

@@ -0,0 +1,56 @@
+
+# PD Multiplexing
+
+
+## Server Arguments
+
+| Argument                     | Type/Default            | Description                                              |
+|-----------------------------|-------------------------|----------------------------------------------------------|
+| `--enable-pdmux`            | flag; default: disabled | Enable PD-Multiplexing (PD running on greenctx stream).  |
+| `--pdmux-config-path <path>`| string path; none       | Path to the PD-Multiplexing YAML config file.            |
+
+### YAML Configuration
+
+Example configuration for an H200 (132 SMs)
+
+```yaml
+# Number of SM groups to divide the GPU into.
+# Includes two default groups:
+#   - Group 0: all SMs for prefill
+#   - Last group: all SMs for decode
+# The number of manual divisions must be (sm_group_num - 2).
+sm_group_num: 8
+
+# Optional manual divisions of SMs.
+# Each entry contains:
+#   - prefill_sm: number of SMs allocated for prefill
+#   - decode_sm: number of SMs allocated for decode
+#   - decode_bs_threshold: minimum decode batch size to select this group
+#
+# The sum of `prefill_sm` and `decode_sm` must equal the total number of SMs.
+# If provided, the number of entries must equal (sm_group_num - 2).
+manual_divisions:
+  - [112, 20, 1]
+  - [104, 28, 5]
+  - [96, 36, 10]
+  - [80, 52, 15]
+  - [64, 68, 20]
+  - [56, 76, 25]
+
+# Divisor for default stream index calculation.
+# Used when manual_divisions are not provided.
+# Formula:
+#   stream_idx = max(
+#       1,
+#       min(sm_group_num - 2,
+#           decode_bs * (sm_group_num - 2) // decode_bs_divisor
+#       )
+#   )
+decode_bs_divisor: 36
+
+# Maximum token budget for split_forward in the prefill stage.
+# Determines how many layers are executed per split_forward.
+# Formula:
+#   forward_count = max(1, split_forward_token_budget // extend_num_tokens)
+split_forward_token_budget: 65536
+```

docs/index.rst

@@ -44,6 +44,7 @@ The core features include:
    advanced_features/quantization.md
    advanced_features/lora.ipynb
    advanced_features/pd_disaggregation.md
+   advanced_features/pd_multiplexing.md
    advanced_features/vlm_query.ipynb
    advanced_features/router.md
    advanced_features/observability.md