constants.rb in passenger-5.0.30

- old
+ new

@@ -74,10 +74,17 @@
 
     # Size limits
     MESSAGE_SERVER_MAX_USERNAME_SIZE = 100
     MESSAGE_SERVER_MAX_PASSWORD_SIZE = 100
     POOL_HELPER_THREAD_STACK_SIZE = 1024 * 256
-    DEFAULT_MBUF_CHUNK_SIZE = 16 * 32
+    # Small mbuf sizes avoid memory overhead (up to 1 blocksize per request), but
+    # also introduce context switching and smaller transfer writes. The size is picked 
+    # to balance this out.
+    DEFAULT_MBUF_CHUNK_SIZE = 1024 * 4
+    # Affects input and output buffering (between app and client). Threshold is picked
+    # such that it fits most output (i.e. html page size, not assets), and allows for
+    # high concurrency with low mem overhead. On the upload side there is a penalty 
+    # but there's no real average upload size anyway so we choose mem safety instead. 
     DEFAULT_FILE_BUFFERED_CHANNEL_THRESHOLD = 1024 * 128
     SERVER_KIT_MAX_SERVER_ENDPOINTS = 4
 
     # Time limits
     PROCESS_SHUTDOWN_TIMEOUT = 60 # In seconds