From owner-svn-src-head@FreeBSD.ORG  Sun Oct 28 21:56:26 2012
Return-Path: <owner-svn-src-head@FreeBSD.ORG>
Delivered-To: svn-src-head@freebsd.org
Received: from mx1.freebsd.org (mx1.freebsd.org [69.147.83.52])
 by hub.freebsd.org (Postfix) with ESMTP id 27B65D8F
 for <svn-src-head@freebsd.org>; Sun, 28 Oct 2012 21:56:26 +0000 (UTC)
 (envelope-from andre@freebsd.org)
Received: from c00l3r.networx.ch (c00l3r.networx.ch [62.48.2.2])
 by mx1.freebsd.org (Postfix) with ESMTP id 7EA5D8FC12
 for <svn-src-head@freebsd.org>; Sun, 28 Oct 2012 21:56:25 +0000 (UTC)
Received: (qmail 93054 invoked from network); 28 Oct 2012 23:33:27 -0000
Received: from c00l3r.networx.ch (HELO [127.0.0.1]) ([62.48.2.2])
 (envelope-sender <andre@freebsd.org>)
 by c00l3r.networx.ch (qmail-ldap-1.03) with SMTP
 for <rpaulo@felyko.com>; 28 Oct 2012 23:33:27 -0000
Message-ID: <508DAA07.9090103@freebsd.org>
Date: Sun, 28 Oct 2012 22:56:23 +0100
From: Andre Oppermann <andre@freebsd.org>
User-Agent: Mozilla/5.0 (Windows NT 6.1; WOW64;
 rv:16.0) Gecko/20121010 Thunderbird/16.0.1
MIME-Version: 1.0
To: Rui Paulo <rpaulo@felyko.com>
Subject: Re: svn commit: r242261 - head/sys/netinet
References: <201210281902.q9SJ272D078237@svn.freebsd.org>
 <6FC10C06-9288-4E2C-A1A2-33C5CC8086C5@felyko.com>
In-Reply-To: <6FC10C06-9288-4E2C-A1A2-33C5CC8086C5@felyko.com>
Content-Type: text/plain; charset=ISO-8859-1; format=flowed
Content-Transfer-Encoding: 7bit
Cc: svn-src-head@freebsd.org, svn-src-all@freebsd.org,
 src-committers@freebsd.org
X-BeenThere: svn-src-head@freebsd.org
X-Mailman-Version: 2.1.14
Precedence: list
List-Id: SVN commit messages for the src tree for head/-current
 <svn-src-head.freebsd.org>
List-Unsubscribe: <http://lists.freebsd.org/mailman/options/svn-src-head>,
 <mailto:svn-src-head-request@freebsd.org?subject=unsubscribe>
List-Archive: <http://lists.freebsd.org/pipermail/svn-src-head>
List-Post: <mailto:svn-src-head@freebsd.org>
List-Help: <mailto:svn-src-head-request@freebsd.org?subject=help>
List-Subscribe: <http://lists.freebsd.org/mailman/listinfo/svn-src-head>,
 <mailto:svn-src-head-request@freebsd.org?subject=subscribe>
X-List-Received-Date: Sun, 28 Oct 2012 21:56:26 -0000

On 28.10.2012 22:34, Rui Paulo wrote:
> On 28 Oct 2012, at 12:02, Andre Oppermann <andre@FreeBSD.org> wrote:
>
>> Author: andre
>> Date: Sun Oct 28 19:02:07 2012
>> New Revision: 242261
>> URL: http://svn.freebsd.org/changeset/base/242261
>>
>> Log:
>>   For retransmits of SYN|ACK from the syncache use the slightly more
>>   aggressive special tcp_syn_backoff[] retransmit schedule instead of
>>   the normal tcp_backoff[] schedule for established connections.
>
>
> How did you came up with the values for tcp_syn_backoff? I obviously
 > understand the aggressiveness, but did you measure any significant
 > improvement in connection establishment time and if so, on what type of links?

I didn't come up with the values.  tcp_syn_backoff[] was introduced
almost 12 years ago by jlemon.  For syncache it got lost somewhere
along the line.

There has been recent talk by some large FreeBSD web server operators
of reducing SYN|ACK retransmit timeouts.  This change fixes a part of
the problem.  The recent RFC on reducing the RTO will fix the other
part.

-- 
Andre