From f70b9c32d5d5b09479b4087bb64f4b95c9821704 Mon Sep 17 00:00:00 2001 From: Corinna Vinschen Date: Thu, 20 Nov 2014 08:29:31 +0000 Subject: [PATCH] * net.cc (fdsock): Change default values for socket buffers on 32 bit to fix performance on 10Gb networks. --- winsup/cygwin/ChangeLog | 5 +++++ winsup/cygwin/net.cc | 11 +++++++++-- 2 files changed, 14 insertions(+), 2 deletions(-) diff --git a/winsup/cygwin/ChangeLog b/winsup/cygwin/ChangeLog index c8419f46c..46cd4c3fa 100644 --- a/winsup/cygwin/ChangeLog +++ b/winsup/cygwin/ChangeLog @@ -1,3 +1,8 @@ +2014-11-20 Iuliu Rus + + * net.cc (fdsock): Change default values for socket buffers on 32 bit + to fix performance on 10Gb networks. + 2014-11-17 Corinna Vinschen * uinfo.cc (pwdgrp::fetch_account_from_windows): Allow fetching of diff --git a/winsup/cygwin/net.cc b/winsup/cygwin/net.cc index 8ff88ba11..5c4959bdf 100644 --- a/winsup/cygwin/net.cc +++ b/winsup/cygwin/net.cc @@ -621,13 +621,20 @@ fdsock (cygheap_fdmanip& fd, const device *dev, SOCKET soc) this is no problem on 64 bit. So we set the default buffer size to the default values in current 3.x Linux versions. + NOTE 3. Setting the window size to 65535 results in extremely bad + performance for apps that send data in multiples of Kb, as they + eventually end up sending 1 byte on the network and naggle + delay + ack kicks in. For example, iperf on a 10Gb network gives only 10 + Mbits/sec with a 65535 send buffer. We want this to be a multiple + of 1k, but since 64k breaks WSADuplicateSocket we use 63Kb. + (*) Maximum normal TCP window size. Coincidence? */ #ifdef __x86_64__ ((fhandler_socket *) fd)->rmem () = 212992; ((fhandler_socket *) fd)->wmem () = 212992; #else - ((fhandler_socket *) fd)->rmem () = 65535; - ((fhandler_socket *) fd)->wmem () = 65535; + ((fhandler_socket *) fd)->rmem () = 64512; + ((fhandler_socket *) fd)->wmem () = 64512; #endif if (::setsockopt (soc, SOL_SOCKET, SO_RCVBUF, (char *) &((fhandler_socket *) fd)->rmem (), sizeof (int)))