[UnifiedTree] Add CP sync (#25395)

Co-authored-by: Zhangheng <hzh0425@apache.org>

python/sglang/srt/mem_cache/unified_radix_cache.py

@@ -304,6 +304,8 @@ class UnifiedRadixCache(KVCacheEventMixin, BasePrefixCache):
         self.session = StreamingSession(inner=self)
 
         self.tp_group = params.tp_cache_group
+        self.attn_cp_group = params.attn_cp_cache_group
+        self.attn_tp_group = params.attn_tp_cache_group
         self.tp_world_size = (
             1
             if self.tp_group is None
@@ -322,6 +324,24 @@ class UnifiedRadixCache(KVCacheEventMixin, BasePrefixCache):
         self.reset()
         logger.info(f"Init Unified RadixTree with components {self.tree_components}")
 
+    def _all_reduce_attn_groups(self, tensor: torch.Tensor, op):
+        reduced = False
+        for group in (self.attn_cp_group, self.attn_tp_group):
+            if group is not None and torch.distributed.get_world_size(group=group) > 1:
+                torch.distributed.all_reduce(tensor, op=op, group=group)
+                reduced = True
+        if not reduced and self.tp_world_size > 1:
+            torch.distributed.all_reduce(tensor, op=op, group=self.tp_group)
+
+    def _barrier_attn_groups(self):
+        waited = False
+        for group in (self.attn_cp_group, self.attn_tp_group):
+            if group is not None and torch.distributed.get_world_size(group=group) > 1:
+                torch.distributed.barrier(group=group)
+                waited = True
+        if not waited and self.tp_world_size > 1:
+            torch.distributed.barrier(group=self.tp_group)
+
     def reset(self) -> None:
         self._reset_full()
 
@@ -2142,12 +2162,9 @@ class UnifiedRadixCache(KVCacheEventMixin, BasePrefixCache):
                 break
             finish_count += 1
 
-        # TP sync: MIN across all ranks for consistent tree updates
+        # Keep cache state transitions identical across CPxTP participants.
         queue_size = torch.tensor(finish_count, dtype=torch.int, device="cpu")
-        if self.tp_world_size > 1:
-            torch.distributed.all_reduce(
-                queue_size, op=torch.distributed.ReduceOp.MIN, group=self.tp_group
-            )
+        self._all_reduce_attn_groups(queue_size, torch.distributed.ReduceOp.MIN)
         finish_count = int(queue_size.item())
 
         # Process completed acks

test/registered/radix_cache/unified_radix_tree/test_unified_radix_cache_kl_cp.py

@@ -0,0 +1,77 @@
+import unittest
+
+from sglang.srt.utils import kill_process_tree
+from sglang.test.ci.ci_register import register_cuda_ci
+from sglang.test.kits.unified_radix_cache_kit import UnifiedRadixTreeTestMixin
+from sglang.test.kl_multiturn_utils import get_input_ids
+from sglang.test.test_utils import (
+    DEFAULT_TIMEOUT_FOR_SERVER_LAUNCH,
+    DEFAULT_URL_FOR_TEST,
+    CustomTestCase,
+    popen_launch_server,
+)
+
+register_cuda_ci(est_time=400, stage="base-c", runner_config="4-gpu-h100")
+
+QWEN3_30B_MODEL = "Qwen/Qwen3-30B-A3B-FP8"
+
+
+class TestUnifiedQwen3HiCacheCP(UnifiedRadixTreeTestMixin, CustomTestCase):
+    """Qwen3-30B-A3B-FP8 + HiCache + CP + UnifiedRadixCache."""
+
+    hicache_io_backend = "direct"
+    hicache_mem_layout = "page_first_direct"
+    max_running_requests = 32
+    kl_threshold = 0.005
+    gsm8k_threshold = 0.7
+    mmlu_threshold = 0.7
+
+    @classmethod
+    def setUpClass(cls):
+        cls.model = QWEN3_30B_MODEL
+        cls.base_url = DEFAULT_URL_FOR_TEST
+        cls.process = popen_launch_server(
+            cls.model,
+            cls.base_url,
+            timeout=DEFAULT_TIMEOUT_FOR_SERVER_LAUNCH,
+            other_args=[
+                "--trust-remote-code",
+                "--tp-size",
+                "4",
+                "--moe-dp-size",
+                "1",
+                "--ep-size",
+                "4",
+                "--attn-cp-size",
+                "2",
+                "--enable-prefill-context-parallel",
+                "--mem-fraction-static",
+                "0.8",
+                "--cuda-graph-max-bs",
+                "32",
+                "--max-running-requests",
+                str(cls.max_running_requests),
+                "--disable-piecewise-cuda-graph",
+                "--model-loader-extra-config",
+                '{"enable_multithread_load": true, "num_threads": 64}',
+                "--enable-hierarchical-cache",
+                "--hicache-ratio",
+                "2",
+                "--hicache-write-policy",
+                "write_through",
+                "--hicache-io-backend",
+                cls.hicache_io_backend,
+                "--hicache-mem-layout",
+                cls.hicache_mem_layout,
+            ],
+            env={"SGLANG_ENABLE_UNIFIED_RADIX_TREE": "1"},
+        )
+        cls.input_ids = get_input_ids(cls.model, num_samples=18)
+
+    @classmethod
+    def tearDownClass(cls):
+        kill_process_tree(cls.process.pid)
+
+
+if __name__ == "__main__":
+    unittest.main()