Date: Sun, 28 Oct 2012 22:56:23 +0100 From: Andre Oppermann <andre@freebsd.org> To: Rui Paulo <rpaulo@felyko.com> Cc: svn-src-head@freebsd.org, svn-src-all@freebsd.org, src-committers@freebsd.org Subject: Re: svn commit: r242261 - head/sys/netinet Message-ID: <508DAA07.9090103@freebsd.org> In-Reply-To: <6FC10C06-9288-4E2C-A1A2-33C5CC8086C5@felyko.com> References: <201210281902.q9SJ272D078237@svn.freebsd.org> <6FC10C06-9288-4E2C-A1A2-33C5CC8086C5@felyko.com>
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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
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