Lower page size in PySpark tests

Author: JoshRosen

python/pyspark/java_gateway.py

@@ -52,7 +52,11 @@ def launch_gateway():
         script = "./bin/spark-submit.cmd" if on_windows else "./bin/spark-submit"
         submit_args = os.environ.get("PYSPARK_SUBMIT_ARGS", "pyspark-shell")
         if os.environ.get("SPARK_TESTING"):
-            submit_args = "--conf spark.ui.enabled=false " + submit_args
+            submit_args = ' '.join([
+                "--conf spark.ui.enabled=false",
+                "--conf spark.buffer.pageSize=4mb",
+                submit_args
+            ])
         command = [os.path.join(SPARK_HOME, script)] + shlex.split(submit_args)
 
         # Start a socket that will be used by PythonGatewayServer to communicate its port to us