From mboxrd@z Thu Jan 1 00:00:00 1970 From: Rick Jones Subject: Re: TCP rx window autotuning harmful at LAN context Date: Mon, 09 Mar 2009 17:34:47 -0700 Message-ID: <49B5B5A7.8090502@hp.com> References: <20090309112521.GB37984@bts.sk> <1e41a3230903091101u536a3b3bv7f0dd9da6891781e@mail.gmail.com> <20090309200505.GA58375@bts.sk> <20090309.170927.130334650.davem@davemloft.net> Mime-Version: 1.0 Content-Type: text/plain; charset=us-ascii; format=flowed Content-Transfer-Encoding: 7bit Cc: md@bts.sk, netdev@vger.kernel.org To: David Miller Return-path: Received: from g1t0028.austin.hp.com ([15.216.28.35]:25200 "EHLO g1t0028.austin.hp.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1752759AbZCJAez (ORCPT ); Mon, 9 Mar 2009 20:34:55 -0400 In-Reply-To: <20090309.170927.130334650.davem@davemloft.net> Sender: netdev-owner@vger.kernel.org List-ID: If I recall correctly, when I have asked about this behaviour in the past, I was told that the autotuning receiver would always try to offer the sender 2X what the receiver thought the sender's cwnd happened to be. Is my recollection incorrect, or is this then: [root@dl5855 ~]# netperf -t omni -H sut42 -- -k foo -s 128K OMNI TEST from 0.0.0.0 (0.0.0.0) port 0 AF_INET to sut42.west (10.208.0.45) port 0 AF_INET THROUGHPUT=941.30 LSS_SIZE_REQ=131072 LSS_SIZE=262142 LSS_SIZE_END=262142 RSR_SIZE_REQ=-1 RSR_SIZE=87380 RSR_SIZE_END=3900000 not intended behaviour? LSS == Local Socket Send; RSR == Remote Socket Receive. dl5855 is running RHEL 5.2 (2.6.18-92.el5) sut42 is running a nf-next-2.6 about two or three weeks old with some of the 32-core scaling patches applied (2.6.29-rc5-nfnextconntrack) I'm assuming that by setting the SO_SNDBUF on the netperf (sending) side to 128K/256K that will be the limit on what it will ever put out onto the connection at one time, but by the end of the 10 second test over the local GbE LAN the receiver's autotuned SO_RCVBUF has grown to 3900000. rick jones