From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S261366AbVGVUIQ (ORCPT ); Fri, 22 Jul 2005 16:08:16 -0400 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S262149AbVGVUIQ (ORCPT ); Fri, 22 Jul 2005 16:08:16 -0400 Received: from dsl027-180-168.sfo1.dsl.speakeasy.net ([216.27.180.168]:4299 "EHLO sunset.davemloft.net") by vger.kernel.org with ESMTP id S261366AbVGVUIN (ORCPT ); Fri, 22 Jul 2005 16:08:13 -0400 Date: Fri, 22 Jul 2005 13:08:16 -0700 (PDT) Message-Id: <20050722.130816.91445335.davem@davemloft.net> To: smfltc@us.ibm.com Cc: linux-kernel@vger.kernel.org, samba-technical@lists.samba.org, netdev@vger.kernel.org Subject: Re: slow tcp acks on loopback device From: "David S. Miller" In-Reply-To: <1122062219.29258.12.camel@stevef95.austin.ibm.com> References: <1122062219.29258.12.camel@stevef95.austin.ibm.com> X-Mailer: Mew version 4.2 on Emacs 21.4 / Mule 5.0 (SAKAKI) Mime-Version: 1.0 Content-Type: Text/Plain; charset=us-ascii Content-Transfer-Encoding: 7bit Sender: linux-kernel-owner@vger.kernel.org X-Mailing-List: linux-kernel@vger.kernel.org From: Steve French Date: 22 Jul 2005 14:56:59 -0500 > Noticing that the loopback device (at least on RHEL4) has an unfortunate > mtu size 16384 (which is about 50 bytes too small for SMB read > responses), I did try increasing the MTU slightly. Changing that to > 18000 did avoid the fragmentation and the 40ms delay - but what puzzled > me was why setting TCP_NODELAY after the socket was created did not > eliminate the delay on the ack and if there is a way to avoid the huge > tcp ack delay by either doing something else to force client acking > immediately or to do something on the client side of the stack to get > the server to send the whole 16K+ frame - it looks like the tcp windows > is 32K if the value in the tcp acks in the network trace is to be > trusted. TCP_NODELAY does not control ACK generation, instead it modifies the Nagle algorithm behavior when sending data packets. Please take networking discussions to netdev@vger.kernel.org which is where the networking developers are.