From mboxrd@z Thu Jan 1 00:00:00 1970 From: Rick Jones Subject: Re: [RFC] tcp: use order-3 pages in tcp_sendmsg() Date: Thu, 20 Sep 2012 10:10:43 -0700 Message-ID: <505B4E13.5000501@hp.com> References: <20120917.121243.1665284878800146060.davem@davemloft.net> <1347901326.26523.149.camel@edumazet-glaptop> <1347901493.26523.151.camel@edumazet-glaptop> <20120917.130732.1894375657044880827.davem@davemloft.net> <1348067659.26523.949.camel@edumazet-glaptop> <1348119475.31352.60.camel@edumazet-glaptop> Mime-Version: 1.0 Content-Type: text/plain; charset=UTF-8; format=flowed Content-Transfer-Encoding: 7bit Cc: Vijay Subramanian , David Miller , netdev@vger.kernel.org To: Eric Dumazet Return-path: Received: from g1t0029.austin.hp.com ([15.216.28.36]:37184 "EHLO g1t0029.austin.hp.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751424Ab2ITRKr (ORCPT ); Thu, 20 Sep 2012 13:10:47 -0400 In-Reply-To: <1348119475.31352.60.camel@edumazet-glaptop> Sender: netdev-owner@vger.kernel.org List-ID: On 09/19/2012 10:37 PM, Eric Dumazet wrote: > loopback is lossless, so its always surprising we can have TCP > retransmits on this medium ;) Is it lossless? raj@tardy:~/netperf2_trunk$ netstat -s | grep pru 19 packets pruned from receive queue because of socket buffer overrun raj@tardy:~/netperf2_trunk$ src/netperf -t TCP_RR -- -b 256 -D -o burst_size,local_transport_retrans,remote_transport_retrans MIGRATED TCP REQUEST/RESPONSE TEST from 0.0.0.0 (0.0.0.0) port 0 AF_INET to localhost.localdomain () port 0 AF_INET : nodelay : histogram : demo : first burst 256 Initial Burst Requests,Local Transport Retransmissions,Remote Transport Retransmissions 256,151,94 raj@tardy:~/netperf2_trunk$ netstat -s | grep pru 26 packets pruned from receive queue because of socket buffer overrun raj@tardy:~/netperf2_trunk$ uname -a Linux tardy 2.6.38-16-generic #67-Ubuntu SMP Thu Sep 6 17:58:38 UTC 2012 x86_64 x86_64 x86_64 GNU/Linux Admittedly, my test is on an older kernel, but have things changed in this regard since then? I had to get a bit more contrived on a later kernel in a VM (vs what is running directly on my workstation): raj@tardy-ubuntu-1204:~$ netstat -s | grep -e prune -e retrans 1 segments retransmited 4 packets pruned from receive queue because of socket buffer overrun 1 fast retransmits raj@tardy-ubuntu-1204:~$ netperf -t TCP_RR -- -b 1024 -D -S 16K -o local_transport_retrans,remote_transport_retrans MIGRATED TCP REQUEST/RESPONSE TEST from 0.0.0.0 (0.0.0.0) port 0 AF_INET to localhost () port 0 AF_INET : nodelay : demo : first burst 1024 Local Transport Retransmissions,Remote Transport Retransmissions 1,0 raj@tardy-ubuntu-1204:~$ netstat -s | grep -e prune -e retrans 2 segments retransmited 7 packets pruned from receive queue because of socket buffer overrun 2 fast retransmits raj@tardy-ubuntu-1204:~$ uname -a Linux tardy-ubuntu-1204 3.6.0-rc3+ #7 SMP Mon Sep 10 14:46:05 PDT 2012 x86_64 x86_64 x86_64 GNU/Linux rick