From owner-freebsd-hackers@FreeBSD.ORG Fri Oct 3 09:25:24 2008 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 2FBAA106568D; Fri, 3 Oct 2008 09:25:24 +0000 (UTC) (envelope-from rwatson@FreeBSD.org) Received: from cyrus.watson.org (cyrus.watson.org [65.122.17.42]) by mx1.freebsd.org (Postfix) with ESMTP id F2DD28FC0C; Fri, 3 Oct 2008 09:25:23 +0000 (UTC) (envelope-from rwatson@FreeBSD.org) Received: from fledge.watson.org (fledge.watson.org [65.122.17.41]) by cyrus.watson.org (Postfix) with ESMTP id 880FD46B0D; Fri, 3 Oct 2008 05:25:23 -0400 (EDT) Date: Fri, 3 Oct 2008 10:25:23 +0100 (BST) From: Robert Watson X-X-Sender: robert@fledge.watson.org To: Danny Braniss In-Reply-To: Message-ID: References: <20080926081806.GA19055@icarus.home.lan> <20080926095230.GA20789@icarus.home.lan> User-Agent: Alpine 1.10 (BSF 962 2008-03-14) MIME-Version: 1.0 Content-Type: TEXT/PLAIN; charset=US-ASCII; format=flowed Cc: freebsd-hackers@freebsd.org, Jeremy Chadwick , freebsd-stable@freebsd.org, Claus Guttesen Subject: Re: bad NFS/UDP performance 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, 03 Oct 2008 09:25:24 -0000 On Fri, 3 Oct 2008, Danny Braniss wrote: > gladly, but have no idea how to do LOCK_PROFILING, so some pointers would be > helpfull. The LOCK_PROFILING(9) man page isn't a bad starting point -- I find that the defaults work fine most of the time, so just use them. Turn the enable syscl on just before you begin a run, and turn it off immediately afterwards. Make sure to reset between reruns (rebooting to a new kernel is fine too!). > as a side note, many years ago I checked out NFS/TCP and it was really bad, > I even remember NetApp telling us to drop TCP, but now, things look rather > better. Wonder what caused it. Well, the virtues of TCP become more apparent with higher network speeds, as the logic to fill pipes using TCP, manage flow control, etc, is a lot more sophisticated than what's in the RPC code for using UDP. The downsides to UDP are also becoming more apparent: as network speeds go up, fragmented UDP risks IP ID collisions which could lead to data corruption, or at the very least, dropped packets. We have changed the default for NFSv3 mounts to TCP in 8.x, and talked about doing it for 7.1; unfortunately the timing wasn't quite right, so it most likely will appear in 7.2. Robert N M Watson Computer Laboratory University of Cambridge