From mboxrd@z Thu Jan 1 00:00:00 1970 From: David Miller Subject: Re: setsockopt() Date: Mon, 07 Jul 2008 16:00:29 -0700 (PDT) Message-ID: <20080707.160029.13296246.davem@davemloft.net> References: <20080707142408.43aa2a2e@extreme> <48728B09.1050801@citi.umich.edu> <48729DAD.8010400@hp.com> Mime-Version: 1.0 Content-Type: Text/Plain; charset=us-ascii Content-Transfer-Encoding: 7bit Cc: aglo@citi.umich.edu, shemminger@vyatta.com, netdev@vger.kernel.org, rees@umich.edu, bfields@fieldses.org To: rick.jones2@hp.com Return-path: Received: from 74-93-104-97-Washington.hfc.comcastbusiness.net ([74.93.104.97]:60858 "EHLO sunset.davemloft.net" rhost-flags-OK-FAIL-OK-OK) by vger.kernel.org with ESMTP id S1758070AbYGGXA3 (ORCPT ); Mon, 7 Jul 2008 19:00:29 -0400 In-Reply-To: <48729DAD.8010400@hp.com> Sender: netdev-owner@vger.kernel.org List-ID: From: Rick Jones Date: Mon, 07 Jul 2008 15:50:21 -0700 > I'm still a triffle puzzled/concerned/confused by the extent to which > autotuning will allow the receive window to grow, again based on some > netperf experience thusfar, and patient explanations provided here and > elsewhere, it seems as though autotuning will let things get to 2x what > it thinks the sender's cwnd happens to be. So far under netperf testing > that seems to be the case, and 99 times out of ten my netperf tests will > have the window grow to the max. We need 2x, in order to have a full window during recovery. There was a measurement bug found a few months ago when the google folks were probing in this area, which was fixed by John Heffner. Most of which had to deal with TSO subtleties. -------------------- commit 246eb2af060fc32650f07203c02bdc0456ad76c7 Author: John Heffner Date: Tue Apr 29 03:13:52 2008 -0700 tcp: Limit cwnd growth when deferring for GSO This fixes inappropriately large cwnd growth on sender-limited flows when GSO is enabled, limiting cwnd growth to 64k. Signed-off-by: John Heffner Signed-off-by: David S. Miller commit ce447eb91409225f8a488f6b7b2a1bdf7b2d884f Author: John Heffner Date: Tue Apr 29 03:13:02 2008 -0700 tcp: Allow send-limited cwnd to grow up to max_burst when gso disabled This changes the logic in tcp_is_cwnd_limited() so that cwnd may grow up to tcp_max_burst() even when sk_can_gso() is false, or when sysctl_tcp_tso_win_divisor != 0. Signed-off-by: John Heffner Signed-off-by: David S. Miller -------------------- Setting TCP socket buffer via setsockopt() is always wrong. If there is a bug, let's fix it.