[https://nvbugs/5552889][fix] fix: Prevent empty batch when using attention DP with disagg (NVIDIA#8372)

pcastonguay · fredricz-20070104 · commit 413d9b843fa7 · 2025-11-05T10:55:20.000+08:00
Signed-off-by: Patrice Castonguay &lt;55748270+pcastonguay@users.noreply.github.com&gt;
Signed-off-by: Mike Iovine &lt;6158008+mikeiovine@users.noreply.github.com&gt;
Signed-off-by: FredricZ-2007 &lt;226039983+fredricz-20070104@users.noreply.github.com&gt;
diff --git a/tensorrt_llm/_torch/pyexecutor/py_executor.py b/tensorrt_llm/_torch/pyexecutor/py_executor.py
@@ -821,12 +821,7 @@ def _executor_loop_pp(self):
                     f'{len(scheduled_batch.generation_requests)} generation requests'
                 )
 
-                if self.enable_attention_dp:
-                    tp_batch_sizes = self.dist.tp_allgather(
-                        scheduled_batch.batch_size)
-                    can_queue = 0 not in tp_batch_sizes
-                else:
-                    can_queue = scheduled_batch.batch_size > 0
+                can_queue = self._can_queue(scheduled_batch)
 
                 if not can_queue:
                     self.micro_batches[microbatch_id] = None
@@ -1004,6 +999,16 @@ def wait_on_pp_send_handles(self, microbatch_id):
             self.send_handles[microbatch_id].wait()
             self.send_handles[microbatch_id] = None
 
+    def _can_queue(self, scheduled_batch):
+
+        if self.enable_attention_dp:
+            tp_batch_sizes = self.dist.tp_allgather(scheduled_batch.batch_size)
+            can_queue = 0 not in tp_batch_sizes
+        else:
+            can_queue = scheduled_batch.batch_size > 0
+
+        return can_queue
+
     def _prepare_and_schedule_batch(self):
         new_requests = self._fetch_and_activate_new_requests()
         if self.should_stop_processing:
@@ -1126,8 +1131,8 @@ def _executor_loop(self):
 
                 finished_requests = []
 
-                if scheduled_batch.batch_size > 0 or (
-                        self.enable_attention_dp and self.dist.tp_size > 1):
+                can_queue = self._can_queue(scheduled_batch)
+                if can_queue:
                     if self.kv_cache_transceiver:
                         # For generation requests which have completed KV cache transfer
                         self._prepare_disagg_gen_transmission_complete(
@@ -1139,8 +1144,11 @@ def _executor_loop(self):
 
                     self._kv_connector_start_batch(scheduled_batch)
 
-                if scheduled_batch.batch_size > 0 or (
-                        self.enable_attention_dp and self.dist.tp_size > 1):
+                # if using a kv connector, we need to call can_queue again since scheduled_batch might have changed
+                if self.kv_connector_manager:
+                    can_queue = self._can_queue(scheduled_batch)
+
+                if can_queue:
                     # init_disagg_gen_requests must be before drafter loop, otherwise draft requests do not have initialized matchers.
                     # init_disagg_gen_requests must be before engine forward, where the prev_seq_slot is updated.
                     if self.guided_decoder is not None:
@@ -1298,7 +1306,8 @@ def _executor_loop_overlap(self):
 
                 self._pause_requests(scheduled_batch.paused_requests)
 
-                if scheduled_batch.batch_size > 0:
+                can_queue = self._can_queue(scheduled_batch)
+                if can_queue:
                     if self.kv_cache_transceiver:
                         # For generation requests which have completed KV cache transfer
                         self._prepare_disagg_gen_transmission_complete(
@@ -1307,7 +1316,11 @@ def _executor_loop_overlap(self):
 
                     self._kv_connector_start_batch(scheduled_batch)
 
-                if scheduled_batch.batch_size > 0:
+                # if using a kv connector, we need to call can_queue again since scheduled_batch might have changed
+                if self.kv_connector_manager:
+                    can_queue = self._can_queue(scheduled_batch)
+
+                if can_queue:
 
                     # The generation requests that are do not have batch_idx,
                     # needs to be in front of the batch due to the assumptions
diff --git a/tests/integration/defs/disaggregated/test_configs/disagg_config_deepseek_v3_lite_empty_batch.yaml b/tests/integration/defs/disaggregated/test_configs/disagg_config_deepseek_v3_lite_empty_batch.yaml
@@ -0,0 +1,61 @@
+hostname: localhost
+port: 8000
+model: DeepSeek-V3-Lite/bf16
+backend: "pytorch"
+context_servers:
+  num_instances: 1
+  build_config:
+    max_batch_size: 10
+    max_num_tokens: 512
+    max_seq_len: 768
+  max_batch_size: 10
+  max_num_tokens: 512
+  max_seq_len: 768
+  tensor_parallel_size: 2
+  moe_expert_parallel_size: 2
+  enable_attention_dp: true
+  pipeline_parallel_size: 1
+  print_iter_log: true
+  cuda_graph_config: null
+  disable_overlap_scheduler: true
+  kv_cache_config:
+    enable_block_reuse: false
+    free_gpu_memory_fraction: 0.05
+    max_tokens: 512
+  cache_transceiver_config:
+    max_tokens_in_buffer: 8448
+    backend: DEFAULT
+  urls:
+      - "localhost:8001"
+generation_servers:
+  num_instances: 1
+  build_config:
+    max_batch_size: 1
+    max_num_tokens: 2048
+    max_seq_len: 2560
+  tensor_parallel_size: 1
+  moe_expert_parallel_size: 1
+  enable_attention_dp: false
+  enable_lm_head_tp_in_adp: false
+  pipeline_parallel_size: 1
+  max_batch_size: 1
+  max_num_tokens: 2048
+  max_seq_len: 2560
+  cuda_graph_config:
+    enable_padding: true
+    batch_sizes:
+    - 1
+  print_iter_log: true
+  kv_cache_config:
+    enable_block_reuse: false
+    free_gpu_memory_fraction: 0.7
+    max_tokens: 2560
+  moe_config:
+    backend: CUTLASS
+  cache_transceiver_config:
+    max_tokens_in_buffer: 8448
+    backend: DEFAULT
+  stream_interval: 1
+  num_postprocess_workers: 1
+  urls:
+      - "localhost:8002"
diff --git a/tests/integration/defs/disaggregated/test_disaggregated.py b/tests/integration/defs/disaggregated/test_disaggregated.py
@@ -261,6 +261,10 @@ def get_test_config(test_desc, example_dir, test_root):
         (4,
          f"{test_configs_root}/disagg_config_ctxtp1_gentp1_deepseek_v3_lite_one_mtp_ctxpp2_gentp2.yaml"
          ),
+        "deepseek_v3_lite_bf16_empty_batch":
+        (3,
+         f"{test_configs_root}/disagg_config_deepseek_v3_lite_empty_batch.yaml"
+         ),
     }
 
     if test_desc not in config_map:
@@ -1530,14 +1534,19 @@ def run_disaggregated_benchmark(example_dir,
                                 benchmark_model_root,
                                 shared_gpt_path,
                                 env=None,
-                                cwd=None):
+                                cwd=None,
+                                num_ranks=2,
+                                random_input_len=16,
+                                random_output_len=64,
+                                num_prompts=100,
+                                max_concurrency=32,
+                                skip_warmup=False):
     """Run disaggregated test with given configuration."""
     run_env = env.copy()
     run_env["UCX_TLS"] = "^ib"
-    num_rank = 2
     workers_cmd = [
         'mpirun', '--allow-run-as-root', '--oversubscribe', '-n',
-        str(num_rank), 'trtllm-serve', 'disaggregated_mpi_worker', '-c',
+        str(num_ranks), 'trtllm-serve', 'disaggregated_mpi_worker', '-c',
         config_file
     ]
 
@@ -1589,15 +1598,15 @@ def run_disaggregated_benchmark(example_dir,
                 '--dataset-path',
                 shared_gpt_path,
                 '--random-input-len',
-                '256',
+                str(random_input_len),
                 '--random-output-len',
-                '64',
+                str(random_output_len),
                 '--random-prefix-len',
                 '0',
                 '--num-prompts',
-                '320',
+                str(num_prompts),
                 '--max-concurrency',
-                '32',
+                str(max_concurrency),
                 '--host',
                 'localhost',
                 '--port',
@@ -1608,7 +1617,8 @@ def run_disaggregated_benchmark(example_dir,
                 'e2el,ttft',
             ]
             # warm up
-            check_call(benchmark_cmd, env=env)
+            if not skip_warmup:
+                check_call(benchmark_cmd, env=env)
             output = check_output(benchmark_cmd, env=env)
             e2el_pattern = r"Median E2EL \(ms\):\s*(\d+\.?\d*)"
             ttft_pattern = r"Median TTFT \(ms\):\s*(\d+\.?\d*)"
@@ -1718,3 +1728,43 @@ def test_disaggregated_benchmark_on_diff_backends(
 
     assert ucx_e2el > 0 and nixl_e2el > 0 and nixl_e2el < 1.05 * ucx_e2el
     assert ucx_ttft > 0 and nixl_ttft > 0 and nixl_ttft < 1.05 * ucx_ttft
+
+
+@pytest.mark.parametrize("benchmark_model_root", ['DeepSeek-V3-Lite-bf16'],
+                         indirect=True)
+def test_disaggregated_deepseek_v3_lite_bf16_empty_batch(
+        disaggregated_example_root, llm_venv, benchmark_model_root,
+        benchmark_root, shared_gpt_path):
+
+    src_dst_dict = {
+        benchmark_model_root:
+        f"{llm_venv.get_working_directory()}/DeepSeek-V3-Lite/bf16",
+    }
+    for src, dst in src_dst_dict.items():
+        if not os.path.islink(dst):
+            os.makedirs(os.path.dirname(dst), exist_ok=True)
+            os.symlink(src, dst, target_is_directory=True)
+
+    test_desc = "deepseek_v3_lite_bf16_empty_batch"
+    num_ranks, config_file = get_test_config(test_desc,
+                                             disaggregated_example_root,
+                                             os.path.dirname(__file__))
+
+    env = llm_venv._new_env.copy()
+    e2el, ttft = run_disaggregated_benchmark(
+        disaggregated_example_root,
+        config_file,
+        benchmark_root,
+        benchmark_model_root,
+        shared_gpt_path,
+        env=env,
+        cwd=llm_venv.get_working_directory(),
+        num_ranks=num_ranks,
+        num_prompts=10,
+        max_concurrency=10,
+        random_input_len=384,
+        random_output_len=1536,
+        skip_warmup=True)
+    print(f"E2EL: {e2el} ms, TTFT: {ttft} ms")
+
+    assert e2el > 0 and ttft > 0
diff --git a/tests/integration/test_lists/test-db/l0_dgx_h100.yml b/tests/integration/test_lists/test-db/l0_dgx_h100.yml
@@ -158,6 +158,7 @@ l0_dgx_h100:
   - disaggregated/test_disaggregated.py::test_disaggregated_deepseek_v3_lite_fp8_overlap_cuda_graph[DeepSeek-V3-Lite-fp8]
   - disaggregated/test_disaggregated.py::test_disaggregated_deepseek_v3_lite_bf16_cache_aware_balance[DeepSeek-V3-Lite-bf16]
   - disaggregated/test_disaggregated.py::test_disaggregated_deepseek_v3_lite_bf16_conditional[DeepSeek-V3-Lite-bf16]
+  - disaggregated/test_disaggregated.py::test_disaggregated_deepseek_v3_lite_bf16_empty_batch[DeepSeek-V3-Lite-bf16]
   - accuracy/test_disaggregated_serving.py::TestDeepSeekV3Lite::test_guided_decoding[xgrammar-mtp_nextn=2]
   - disaggregated/test_disaggregated.py::test_disaggregated_deepseek_v3_lite_fp8_ctxpp2_gentp2_one_mtp[DeepSeek-V3-Lite-fp8]
   - disaggregated/test_workers.py::test_workers_conditional_disaggregation_deepseek_v3_lite_bf16[DeepSeek-V3-Lite-bf16]
