fix zero overhead bug when kvcache oom and schedule

vllm/sequence.py

@@ -14,6 +14,7 @@ from typing import Any, Callable, Optional, Union
 import msgspec
 import torch
 
+from vllm import envs
 from vllm.inputs import SingletonInputs
 from vllm.lora.request import LoRARequest
 from vllm.multimodal import MultiModalKwargs, MultiModalPlaceholderDict
@@ -809,6 +810,7 @@ class SequenceGroup:
 
     def set_last_token_time(self, now: float) -> None:
         """Sets the last token time for Request level timings."""
+        if not envs.VLLM_ZERO_OVERHEAD:
             # If still in prefill phase, assertion fails.
             assert not self.is_prefill(), (
                 "seq_group.set_last_token_time() should not be called "
@@ -818,6 +820,7 @@ class SequenceGroup:
 
     def get_last_token_latency(self) -> float:
         """Returns the latency of the last token."""
+        if not envs.VLLM_ZERO_OVERHEAD:
             assert not self.is_prefill(), (
                 "seq_group.get_last_token_latency() should not be called "
                 "if the seq_group is in prefill phase.")