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.

1 files changed, 8 insertions, 0 deletions

diff --git a/net/server_epoll.lua b/net/server_epoll.lua
index 49ad48ea..ef021851 100644
--- a/net/server_epoll.lua
+++ b/net/server_epoll.lua
@@ -66,6 +66,9 @@ local default_config = { __index = {
 	-- 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 @@ function interface:onwritable()
 		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 @@ function interface:write(data)
 		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