fix: change performance log directory to cache path (#13482)

Co-authored-by: Mick <mickjagger19@icloud.com>

python/sglang/multimodal_gen/runtime/utils/performance_logger.py

@@ -10,13 +10,28 @@ from typing import Any
 
 from dateutil.tz import UTC
 
-LOG_DIR = os.environ.get("SGLANG_PERF_LOG_DIR")
-if LOG_DIR:
-    LOG_DIR = os.path.abspath(LOG_DIR)
-elif LOG_DIR is None:  # Not set
-    project_root = os.path.abspath(os.path.join(os.path.dirname(__file__), "../../../"))
-    LOG_DIR = os.path.join(project_root, "logs")
-# if LOG_DIR is "", it will remain "", disabling file logging.
+
+def get_diffusion_perf_log_dir() -> str:
+    """
+    Determines the directory for performance logs, centralizing the logic.
+
+    Resolution order:
+    1. SGLANG_PERF_LOG_DIR environment variable, if set and not empty.
+    2. Default to ~/.cache/sglang/logs if the environment variable is not set.
+    3. Returns an empty string if SGLANG_PERF_LOG_DIR is set to an empty string,
+       which effectively disables file logging.
+    """
+    log_dir = os.environ.get("SGLANG_PERF_LOG_DIR")
+    if log_dir:
+        return os.path.abspath(log_dir)
+    if log_dir is None:
+        # Not set, use default
+        return os.path.join(os.path.expanduser("~/.cache/sglang"), "logs")
+    # Is set, but is an empty string
+    return ""
+
+
+LOG_DIR = get_diffusion_perf_log_dir()
 
 # Configure a specific logger for performance metrics
 perf_logger = logging.getLogger("performance")

python/sglang/multimodal_gen/test/server/diffusion_server.py

@@ -105,7 +105,7 @@ class ServerManager:
 
     def start(self) -> ServerContext:
         """Start the diffusion server and wait for readiness."""
-        log_dir, perf_log_path = prepare_perf_log(Path(__file__))
+        log_dir, perf_log_path = prepare_perf_log()
 
         safe_model_name = self.model.replace("/", "_")
         stdout_path = (

python/sglang/multimodal_gen/test/test_utils.py

@@ -17,6 +17,9 @@ from PIL import Image
 from sglang.multimodal_gen.configs.sample.base import DataType
 from sglang.multimodal_gen.runtime.utils.common import get_bool_env_var
 from sglang.multimodal_gen.runtime.utils.logging_utils import init_logger
+from sglang.multimodal_gen.runtime.utils.performance_logger import (
+    get_diffusion_perf_log_dir,
+)
 
 logger = init_logger(__name__)
 
@@ -107,12 +110,15 @@ def check_image_size(ut, image, width, height):
     ut.assertEqual(image.size, (width, height))
 
 
-def get_perf_log_dir(start_file: Path) -> Path:
-    """Mirror runtime/utils/performance_logger.py behaviour for locating logs."""
-    this_file = start_file.resolve()
-    root_logs = this_file.parents[3] / "logs"
-    fallback = this_file.parents[2] / "logs"
-    return root_logs if root_logs.exists() or not fallback.exists() else fallback
+def get_perf_log_dir() -> Path:
+    """Gets the performance log directory from the centralized sglang utility."""
+    log_dir_str = get_diffusion_perf_log_dir()
+    if not log_dir_str:
+        raise RuntimeError(
+            "Performance logging is disabled (SGLANG_PERF_LOG_DIR is empty), "
+            "but a test tried to access the log directory."
+        )
+    return Path(log_dir_str)
 
 
 def _ensure_log_path(log_dir: Path) -> Path:
@@ -129,9 +135,9 @@ def clear_perf_log(log_dir: Path) -> Path:
     return log_path
 
 
-def prepare_perf_log(start_file: Path) -> tuple[Path, Path]:
+def prepare_perf_log() -> tuple[Path, Path]:
     """Convenience helper to resolve and clear the perf log in one call."""
-    log_dir = get_perf_log_dir(start_file)
+    log_dir = get_perf_log_dir()
     log_path = clear_perf_log(log_dir)
     return log_dir, log_path