From owner-freebsd-hackers@FreeBSD.ORG Fri Nov 13 02:08:36 2009 Return-Path: Delivered-To: freebsd-hackers@freebsd.org Received: from mx1.freebsd.org (mx1.freebsd.org [IPv6:2001:4f8:fff6::34]) by hub.freebsd.org (Postfix) with ESMTP id E7E1E1065672 for ; Fri, 13 Nov 2009 02:08:36 +0000 (UTC) (envelope-from sh@visor.slugabed.org) Received: from visor.slugabed.org (visor.slugabed.org [64.69.77.108]) by mx1.freebsd.org (Postfix) with ESMTP id CA4D38FC0A for ; Fri, 13 Nov 2009 02:08:36 +0000 (UTC) Received: from visor.slugabed.org (sh@localhost [127.0.0.1]) by visor.slugabed.org (8.13.8/8.13.8) with ESMTP id nAD28ZUg074628 for ; Thu, 12 Nov 2009 18:08:35 -0800 (PST) (envelope-from sh@visor.slugabed.org) Received: (from sh@localhost) by visor.slugabed.org (8.13.8/8.13.8/Submit) id nAD28ZEV074627 for freebsd-hackers@freebsd.org; Thu, 12 Nov 2009 18:08:35 -0800 (PST) (envelope-from sh) Date: Thu, 12 Nov 2009 18:08:35 -0800 From: Sean Hamilton To: freebsd-hackers@freebsd.org Message-ID: <20091113020835.GE12442@visor.slugabed.org> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline User-Agent: Mutt/1.5.20 (2009-06-14) Subject: NUMA support; tweaking TCP for GPRS X-BeenThere: freebsd-hackers@freebsd.org X-Mailman-Version: 2.1.5 Precedence: list List-Id: Technical Discussions relating to FreeBSD List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , X-List-Received-Date: Fri, 13 Nov 2009 02:08:37 -0000 Greetings -hackers, I have two unrelated questions. First, what is the status of NUMA support in FreeBSD? Is there a performance penalty on Nehalem-class systems, compared with Linux, which advertises NUMA awareness? Google seems to turn up very little on this subject. Second, I am using a FreeBSD server to talk to equipment which has a GPRS internet connection. This is fairly high latency (approximately one second RTT) and is prone to bursts of packet loss, or bursts of extremely high latency -- perhaps up to a minute. These intervals cause many retransmissions, which I presume is a good strategy over the internet, but not so good for GPRS. For my application, latency is mostly irrelevant. However, data over GPRS is very expensive, so I would like to reduce as much as possible the number of TCP retransmissions made on the FreeBSD side, possibly at the expense of latency. So, I am looking for suggestions on how to achieve this, via sysctl, setsockopt, etc. There seems to be a lot of literature regarding TCP tuning, but usually the focus is on improving performance, not reducing network traffic. The "rexmit_min" and "rexmit_sop" sysctls mentioned in tcp(4) seem interesting, but it's not clear to me exactly how they might be adjusted for this purpose. Thanks in advance, -- Sean Hamilton