Break TCPConnection's _read_buffer_size into 3 different variables

Prior to this change, _read_buffer_size was used for 3 different
purposes:

- Sizing the read buffer
- Controlling how many bytes to read before yielding the CPU
- Controlling how many bytes to write before yielding the CPU

This commit provides 3 different variables, one for each of the 3
possible usages.

Closes #3186

Author: SeanTAllen

packages/net/tcp_connection.pony

@@ -216,6 +216,9 @@ actor TCPConnection
 
   let _read_buffer_size: USize
 
+  let _yield_after_reading: USize
+  let _yield_after_writing: USize
+
   var _expect: USize = 0
 
   var _muted: Bool = false
@@ -226,14 +229,18 @@ actor TCPConnection
     host: String,
     service: String,
     from: String = "",
-    read_buffer_size: USize = 16384)
+    read_buffer_size: USize = 16384,
+    yield_after_reading: USize = 16384,
+    yield_after_writing: USize = 16384)
   =>
     """
     Connect via IPv4 or IPv6. If `from` is a non-empty string, the connection
     will be made from the specified interface.
     """
     _read_buf = recover Array[U8] .> undefined(read_buffer_size) end
     _read_buffer_size = read_buffer_size
+    _yield_after_reading = yield_after_reading
+    _yield_after_writing = yield_after_writing
     _notify = consume notify
     let asio_flags =
       ifdef not windows then
@@ -252,13 +259,17 @@ actor TCPConnection
     host: String,
     service: String,
     from: String = "",
-    read_buffer_size: USize = 16384)
+    read_buffer_size: USize = 16384,
+    yield_after_reading: USize = 16384,
+    yield_after_writing: USize = 16384)
   =>
     """
     Connect via IPv4.
     """
     _read_buf = recover Array[U8] .> undefined(read_buffer_size) end
     _read_buffer_size = read_buffer_size
+    _yield_after_reading = yield_after_reading
+    _yield_after_writing = yield_after_writing
     _notify = consume notify
     let asio_flags =
       ifdef not windows then
@@ -277,13 +288,17 @@ actor TCPConnection
     host: String,
     service: String,
     from: String = "",
-    read_buffer_size: USize = 16384)
+    read_buffer_size: USize = 16384,
+    yield_after_reading: USize = 16384,
+    yield_after_writing: USize = 16384)
   =>
     """
     Connect via IPv6.
     """
     _read_buf = recover Array[U8] .> undefined(read_buffer_size) end
     _read_buffer_size = read_buffer_size
+    _yield_after_reading = yield_after_reading
+    _yield_after_writing = yield_after_writing
     _notify = consume notify
     let asio_flags =
       ifdef not windows then
@@ -300,7 +315,9 @@ actor TCPConnection
     listen: TCPListener,
     notify: TCPConnectionNotify iso,
     fd: U32,
-    read_buffer_size: USize = 16384)
+    read_buffer_size: USize = 16384,
+    yield_after_reading: USize = 16384,
+    yield_after_writing: USize = 16384)
   =>
     """
     A new connection accepted on a server.
@@ -323,6 +340,8 @@ actor TCPConnection
     _writeable = true
     _read_buf = recover Array[U8] .> undefined(read_buffer_size) end
     _read_buffer_size = read_buffer_size
+    _yield_after_reading = yield_after_reading
+    _yield_after_writing = yield_after_writing
 
     _notify.accepted(this)
 
@@ -648,7 +667,9 @@ actor TCPConnection
       var bytes_to_send: USize = 0
       var bytes_sent: USize = 0
       while _writeable and (_pending_writev_total > 0) do
-        if bytes_sent >= _read_buffer_size then
+        if bytes_sent >= _yield_after_writing then
+          // We've written _yield_after_writing bytes.
+          // Yield and write again later.
           _write_again()
           return false
         end
@@ -861,8 +882,9 @@ actor TCPConnection
             end
           end
 
-          if sum >= _read_buffer_size then
-            // If we've read _read_buffer_size, yield and read again later.
+          if sum >= _yield_after_reading then
+            // If we've read _yield_after_reading bytes
+            // yield and read again later.
             _read_buf_size()
             _read_again()
             _reading = false

packages/net/tcp_listener.pony

@@ -46,14 +46,19 @@ actor TCPListener
   var _count: USize = 0
   var _paused: Bool = false
   var _read_buffer_size: USize
+  let _yield_after_reading: USize
+  let _yield_after_writing: USize
+
 
   new create(
     auth: TCPListenerAuth,
     notify: TCPListenNotify iso,
     host: String = "",
     service: String = "0",
     limit: USize = 0,
-    read_buffer_size: USize = 16384)
+    read_buffer_size: USize = 16384,
+    yield_after_reading: USize = 16384,
+    yield_after_writing: USize = 16384)
   =>
     """
     Listens for both IPv4 and IPv6 connections.
@@ -64,6 +69,8 @@ actor TCPListener
       @pony_os_listen_tcp[AsioEventID](this,
         host.cstring(), service.cstring())
     _read_buffer_size = read_buffer_size
+    _yield_after_reading = yield_after_reading
+    _yield_after_writing = yield_after_writing
     _fd = @pony_asio_event_fd(_event)
     _notify_listening()
 
@@ -73,7 +80,9 @@ actor TCPListener
     host: String = "",
     service: String = "0",
     limit: USize = 0,
-    read_buffer_size: USize = 16384)
+    read_buffer_size: USize = 16384,
+    yield_after_reading: USize = 16384,
+    yield_after_writing: USize = 16384)
   =>
     """
     Listens for IPv4 connections.
@@ -84,6 +93,8 @@ actor TCPListener
       @pony_os_listen_tcp4[AsioEventID](this, host.cstring(),
         service.cstring())
     _read_buffer_size = read_buffer_size
+    _yield_after_reading = yield_after_reading
+    _yield_after_writing = yield_after_writing
     _fd = @pony_asio_event_fd(_event)
     _notify_listening()
 
@@ -93,7 +104,9 @@ actor TCPListener
     host: String = "",
     service: String = "0",
     limit: USize = 0,
-    read_buffer_size: USize = 16384)
+    read_buffer_size: USize = 16384,
+    yield_after_reading: USize = 16384,
+    yield_after_writing: USize = 16384)
   =>
     """
     Listens for IPv6 connections.
@@ -104,6 +117,8 @@ actor TCPListener
       @pony_os_listen_tcp6[AsioEventID](this, host.cstring(),
         service.cstring())
     _read_buffer_size = read_buffer_size
+    _yield_after_reading = yield_after_reading
+    _yield_after_writing = yield_after_writing
     _fd = @pony_asio_event_fd(_event)
     _notify_listening()
 
@@ -211,7 +226,7 @@ actor TCPListener
     """
     try
       TCPConnection._accept(this, _notify.connected(this)?, ns,
-        _read_buffer_size)
+        _read_buffer_size, _yield_after_reading, _yield_after_writing)
       _count = _count + 1
     else
       @pony_os_socket_close[None](ns)