# HG changeset patch
# User Kim Alvefur <zash@zash.se>
# Date 1566949260 -7200
# Node ID e77bf4222fae7c94ab41e51fffc0021d8c01f998
# Parent  eeb711b92da5dc6067bd1a29a22bf2b7319b0c62
net.server_epoll: Add support for opportunistic writes

This tries to flush data to the underlying sockets when receiving
writes. This should lead to fewer timer objects being around. On the
other hand, this leads to more and smaller writes which may translate to
more TCP/IP packets being sent, depending on how the kernel handles
this. This trades throughput for lower latency.

diff -r eeb711b92da5 -r e77bf4222fae net/server_epoll.lua
--- a/net/server_epoll.lua	Sun Aug 25 23:25:42 2019 +0200
+++ b/net/server_epoll.lua	Wed Aug 28 01:41:00 2019 +0200
@@ -66,6 +66,9 @@
 	-- EXPERIMENTAL
 	-- Whether to kill connections in case of callback errors.
 	fatal_errors = false;
+
+	-- Attempt writes instantly
+	opportunistic_writes = false;
 }};
 local cfg = default_config.__index;
 
@@ -413,6 +416,7 @@
 		for i = #buffer, 2, -1 do
 			buffer[i] = nil;
 		end
+		self:set(nil, true);
 		self:setwritetimeout();
 	end
 	if err == "wantwrite" or err == "timeout" then
@@ -439,6 +443,10 @@
 		self.writebuffer = { data };
 	end
 	if not self._write_lock then
+		if cfg.opportunistic_writes then
+			self:onwritable();
+			return #data;
+		end
 		self:setwritetimeout();
 		self:set(nil, true);
 	end