From mboxrd@z Thu Jan 1 00:00:00 1970 From: Rick Jones Subject: Re: TCP funny-ness when over-driving a 1Gbps link. Date: Thu, 19 May 2011 17:24:39 -0700 Message-ID: <1305851079.8149.1127.camel@tardy> References: <4DD59DF2.2070707@candelatech.com> <20110519161827.2ba4b40e@nehalam> <4DD5A5CD.7040303@candelatech.com> <4DD5AAFC.8070509@candelatech.com> <1305849940.8149.1122.camel@tardy> <4DD5B202.7080701@candelatech.com> Reply-To: rick.jones2@hp.com Mime-Version: 1.0 Content-Type: text/plain; charset="UTF-8" Content-Transfer-Encoding: 7bit Cc: Stephen Hemminger , netdev To: Ben Greear Return-path: Received: from g1t0027.austin.hp.com ([15.216.28.34]:29855 "EHLO g1t0027.austin.hp.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1753191Ab1ETAYl (ORCPT ); Thu, 19 May 2011 20:24:41 -0400 In-Reply-To: <4DD5B202.7080701@candelatech.com> Sender: netdev-owner@vger.kernel.org List-ID: > >> [root@i7-965-1 igb]# netstat -an|grep tcp|grep 8.1.1 > >> tcp 0 0 8.1.1.1:33038 0.0.0.0:* LISTEN > >> tcp 0 0 8.1.1.1:33040 0.0.0.0:* LISTEN > >> tcp 0 0 8.1.1.1:33042 0.0.0.0:* LISTEN > >> tcp 0 9328612 8.1.1.2:33039 8.1.1.1:33040 ESTABLISHED > >> tcp 0 17083176 8.1.1.1:33038 8.1.1.2:33037 ESTABLISHED > >> tcp 0 9437340 8.1.1.2:33037 8.1.1.1:33038 ESTABLISHED > >> tcp 0 17024620 8.1.1.1:33040 8.1.1.2:33039 ESTABLISHED > >> tcp 0 19557040 8.1.1.1:33042 8.1.1.2:33041 ESTABLISHED > >> tcp 0 9416600 8.1.1.2:33041 8.1.1.1:33042 ESTABLISHED > > > > I take it your system has higher values for the tcp_wmem value: > > > > net.ipv4.tcp_wmem = 4096 16384 4194304 > > Yes: > [root@i7-965-1 igb]# cat /proc/sys/net/ipv4/tcp_wmem > 4096 16384 50000000 Why?!? Are you trying to get link-rate to Mars or something? (I assume tcp_rmem is similarly set...) If you are indeed doing one 1 GbE, and no more than 100ms then the default (?) of 4194304 should have been more than sufficient. > > and whatever is creating the TCP connections is not making explicit > > setsockopt() calls to set SO_*BUF. > > It is configured not to, but if you know of an independent way to verify > that, I'm interested. You could always strace the code. rick