[Feature] Add initial support for sequence parallelism

python/sglang/bench_latency.py

@@ -115,7 +115,7 @@ def from_cli_args(cls, args: argparse.Namespace):
         )
 
 
-def load_model(server_args, tp_rank):
+def load_model(server_args, tp_rank, sp_rank: int = 0):
     suppress_other_loggers()
     rank_print = print if tp_rank == 0 else lambda *args, **kwargs: None
 
@@ -130,6 +130,8 @@ def load_model(server_args, tp_rank):
         gpu_id=tp_rank,
         tp_rank=tp_rank,
         tp_size=server_args.tp_size,
+        sp_rank=sp_rank,
+        sp_size=server_args.sp_size,
         nccl_port=28888,
         server_args=server_args,
     )
@@ -206,6 +208,8 @@ def extend(reqs, model_runner):
         req_to_token_pool=model_runner.req_to_token_pool,
         token_to_kv_pool=model_runner.token_to_kv_pool,
         tree_cache=None,
+        sp_size=model_runner.sp_size,
+        sp_rank=model_runner.sp_rank,
     )
     batch.prepare_for_extend(model_runner.model_config.vocab_size)
     sample_output, logits_output = model_runner.forward(batch, ForwardMode.EXTEND)
@@ -225,11 +229,12 @@ def correctness_test(
     server_args,
     bench_args,
     tp_rank,
+    sp_rank=0,
 ):
     rank_print = print if tp_rank == 0 else lambda *args, **kwargs: None
 
     # Load the model
-    model_runner, tokenizer = load_model(server_args, tp_rank)
+    model_runner, tokenizer = load_model(server_args, tp_rank, sp_rank)
 
     # Prepare inputs
     input_ids, reqs = prepare_inputs_for_correctness_test(bench_args, tokenizer)
@@ -336,11 +341,12 @@ def latency_test(
     server_args,
     bench_args,
     tp_rank,
+    sp_rank=0,
 ):
     rank_print = print if tp_rank == 0 else lambda *args, **kwargs: None
 
     # Load the model
-    model_runner, tokenizer = load_model(server_args, tp_rank)
+    model_runner, tokenizer = load_model(server_args, tp_rank, sp_rank)
 
     # Prepare inputs for warm up
     reqs = prepare_synthetic_inputs_for_latency_test(
@@ -458,16 +464,18 @@ def main(server_args, bench_args):
         )
 
     if server_args.tp_size == 1:
-        work_func(server_args, bench_args, 0)
+        work_func(server_args, bench_args, 0, 0)
     else:
         workers = []
         for tp_rank in range(server_args.tp_size):
+            sp_rank = tp_rank % server_args.sp_size
             proc = multiprocessing.Process(
                 target=work_func,
                 args=(
                     server_args,
                     bench_args,
                     tp_rank,
+                    sp_rank,
                 ),
             )
             proc.start()

python/sglang/srt/layers/parallel_utils/__init__.py

@@ -0,0 +1 @@
+from .parallel_state import *

python/sglang/srt/layers/parallel_utils/parallel_state.py

@@ -0,0 +1,96 @@
+from typing import List, Optional
+
+import torch
+from vllm.distributed import initialize_model_parallel as vllm_initialize_model_parallel
+from vllm.distributed.parallel_state import (
+    GroupCoordinator,
+    get_tensor_model_parallel_rank,
+    get_tensor_model_parallel_world_size,
+    get_world_group,
+    init_model_parallel_group,
+)
+
+_SP: Optional[GroupCoordinator] = None
+
+
+def get_sp_group():
+    assert _SP is not None, "sequence parallel group is not initialized"
+    return _SP
+
+
+def init_sequence_parallel_group(
+    group_ranks: List[List[int]], local_rank: int, backend: str
+) -> GroupCoordinator:
+    return GroupCoordinator(
+        group_ranks=group_ranks,
+        local_rank=local_rank,
+        torch_distributed_backend=backend,
+        use_pynccl=True,
+    )
+
+
+def initialize_model_parallel(
+    tensor_model_parallel_size: int = 1,
+    pipeline_model_parallel_size: int = 1,
+    sequence_parallel_size: int = 1,
+    backend: Optional[str] = None,
+) -> None:
+    """
+    Initialize model parallel groups and sequence parallel groups.
+
+    For sequence parallelism, we partition SP groups within a TP group, and assign
+    gpus with adjacent ranks to the same SP group. For example, with TP size 8
+    and SP size 2, we have 1 TP group and 4 SP groups:
+    SP groups:
+        [g0, g1], [g2, g3], [g4, g5], [g6, g7]
+    Their KV TP rank:
+        [ 0,  0], [ 1,  1], [ 2,  2], [ 3,  3]
+    Given that we replicate KV heads within the same seq parallel group, we also say that
+    the KV TP size is 4 (8//2), and gpus in each SP group have KV-tp rank from 0 to 3.
+    """
+    assert torch.distributed.is_initialized()
+    world_size: int = torch.distributed.get_world_size()
+    backend = backend or torch.distributed.get_backend(get_world_group().device_group)
+
+    num_sequence_parallel_groups: int = world_size // sequence_parallel_size
+    global _SP
+    assert _SP is None, "sequence parallel group is already initialized"
+    group_ranks = []
+    for i in range(num_sequence_parallel_groups):
+        ranks = list(
+            range(i * sequence_parallel_size, (i + 1) * sequence_parallel_size)
+        )
+        group_ranks.append(ranks)
+    _SP = init_model_parallel_group(group_ranks, get_world_group().local_rank, backend)
+
+    vllm_initialize_model_parallel(
+        tensor_model_parallel_size, pipeline_model_parallel_size, backend
+    )
+
+
+def sequence_parallel_is_initialized():
+    return _SP is not None
+
+
+def get_sequence_parallel_world_size():
+    return get_sp_group().world_size
+
+
+def get_sequence_parallel_rank():
+    return get_sp_group().rank_in_group
+
+
+def get_sequence_parallel_global_rank():
+    return get_tensor_model_parallel_rank()
+
+
+# NOTE: For sequence parallelism, we partition Q tensors along the head dimension.
+# But K/V tensors are partitioned along the head dimension in TP and partitioned
+# along the sequence dimensions in SP. Therefore, their TP size and rank is adjusted
+# accordingly as below.
+def get_kv_tensor_model_parallel_world_size():
+    return get_tensor_model_parallel_world_size() // get_sequence_parallel_world_size()
+
+
+def get_kv_tensor_model_parallel_rank():
+    return get_tensor_model_parallel_rank() // get_sequence_parallel_world_size()