[P/D] Heterogeneous TP (#18833)

Signed-off-by: nicklucche <nlucches@redhat.com>

tests/v1/kv_connector/nixl_integration/run_accuracy_test.sh

@@ -8,7 +8,9 @@ MODELS=(
 
 # Number of prefill and decode instances to create
 NUM_PREFILL_INSTANCES=${NUM_PREFILL_INSTANCES:-1} # Default to 1
-NUM_DECODE_INSTANCES=${NUM_DECODE_INSTANCES:-2}   # Default to 2
+NUM_DECODE_INSTANCES=${NUM_DECODE_INSTANCES:-1}   # Default to 1
+PREFILLER_TP_SIZE=${PREFILLER_TP_SIZE:-1}
+DECODER_TP_SIZE=${DECODER_TP_SIZE:-1}
 
 # Find the git repository root directory
 GIT_ROOT=$(git rev-parse --show-toplevel)
@@ -74,9 +76,10 @@ run_tests_for_model() {
   for i in $(seq 0 $((NUM_PREFILL_INSTANCES-1))); do
     # Calculate GPU ID - we'll distribute across available GPUs
     GPU_ID=$((i % $(get_num_gpus)))
+
     # Calculate port number (base port + instance number)
     PORT=$((8100 + i))
-    # Calculate side channel port
+    # Calculate side channel port. Avoid clash with with TP workers. 
     SIDE_CHANNEL_PORT=$((5559 + i))
 
     echo "Starting prefill instance $i on GPU $GPU_ID, port $PORT"
@@ -87,6 +90,7 @@ run_tests_for_model() {
     --enforce-eager \
     --disable-log-requests \
     --gpu-memory-utilization 0.2 \
+    --tensor-parallel-size $PREFILLER_TP_SIZE \
     --kv-transfer-config '{\"kv_connector\":\"NixlConnector\",\"kv_role\":\"kv_both\"}'"
 
     if [ -n "$model_args" ]; then
@@ -109,7 +113,7 @@ run_tests_for_model() {
     # Calculate port number (base port + instance number)
     PORT=$((8200 + i))
     # Calculate side channel port
-    SIDE_CHANNEL_PORT=$((5659 + i))
+    SIDE_CHANNEL_PORT=$((5659 + i * $DECODER_TP_SIZE))
 
     echo "Starting decode instance $i on GPU $GPU_ID, port $PORT"
 
@@ -119,6 +123,7 @@ run_tests_for_model() {
     --enforce-eager \
     --disable-log-requests \
     --gpu-memory-utilization 0.2 \
+    --tensor-parallel-size $DECODER_TP_SIZE \
     --kv-transfer-config '{\"kv_connector\":\"NixlConnector\",\"kv_role\":\"kv_both\"}'"
 
     if [ -n "$model_args" ]; then

tests/v1/kv_connector/nixl_integration/test_accuracy.py

@@ -14,6 +14,7 @@ RTOL = 0.03
 # Model-specific expected values
 EXPECTED_VALUES = {
     "Qwen/Qwen3-0.6B": 0.41,
+    "deepseek-ai/deepseek-vl2-small": 0.59
 }
 
 SIMPLE_PROMPT = "The best part about working on vLLM is that I got to meet so many people across various different organizations like UCB, Google, and Meta which means",  # noqa: E501

vllm/distributed/kv_transfer/kv_connector/utils.py

@@ -3,11 +3,12 @@
 """
 KV cache helper for store.
 """
+
 import torch
 
 import vllm.envs as envs
 from vllm import _custom_ops as ops
-from vllm.config import VllmConfig
+from vllm.config import VllmConfig, get_current_vllm_config
 from vllm.logger import init_logger
 
 logger = init_logger(__name__)
@@ -90,3 +91,18 @@ class model_aware_kv_ops_helper:
                 layer.self_attn.attn._k_scale,
                 layer.self_attn.attn._v_scale,
             )
+
+
+def get_kv_connector_cache_layout():
+    vllm_config = get_current_vllm_config()
+    kv_config = vllm_config.kv_transfer_config
+    if vllm_config.model_config is None:
+        logger.warning("Unable to detect current VLLM config. " \
+        "Defaulting to NHD kv cache layout.")
+    else:
+        use_mla = vllm_config.model_config.use_mla
+        if not use_mla and kv_config.kv_connector == "NixlConnector":
+            logger.info("NixlConnector detected. Setting KV cache " \
+            "layout to HND for better xfer performance.")
+            return "HND"
+    return "NHD"

vllm/v1/attention/backends/flash_attn.py

@@ -16,6 +16,8 @@ from vllm.attention.ops.merge_attn_states import merge_attn_states
 from vllm.attention.utils.fa_utils import (flash_attn_supports_fp8,
                                            get_flash_attn_version)
 from vllm.config import VllmConfig, get_layers_from_vllm_config
+from vllm.distributed.kv_transfer.kv_connector.utils import (
+    get_kv_connector_cache_layout)
 from vllm.logger import init_logger
 from vllm.platforms import current_platform
 from vllm.utils import cdiv
@@ -70,6 +72,20 @@ class FlashAttentionBackend(AttentionBackend):
             raise ValueError("Block size must be a multiple of 16.")
         return (2, num_blocks, block_size, num_kv_heads, head_size)
 
+    @staticmethod
+    def get_kv_cache_stride_order() -> tuple[int, ...]:
+        # NOTE When running disaggregated PD with NIXL, HND layout is used for
+        # faster transfer. `stride_order` indicates the permutation that gets
+        # us from `get_kv_cache_shape` to the actual memory layout we want.
+        cache_layout = get_kv_connector_cache_layout()
+        if cache_layout == "NHD":
+            stride_order = (0, 1, 2, 3, 4)
+        elif cache_layout == "HND":
+            stride_order = (0, 1, 3, 2, 4)
+        else:
+            raise ValueError("Unknown cache layout format %s.", cache_layout)
+        return stride_order
+
 
 @dataclass
 class FlashAttentionMetadata:

vllm/worker/worker_base.py

@@ -597,6 +597,7 @@ class WorkerWrapperBase:
 
     def initialize_from_config(self, kv_cache_configs: List[Any]) -> None:
         kv_cache_config = kv_cache_configs[self.rpc_rank]
+        with set_current_vllm_config(self.vllm_config):
             self.worker.initialize_from_config(kv_cache_config)  # type: ignore
 
     def init_device(self):