From owner-freebsd-arch@FreeBSD.ORG Sun Mar 20 01:19:46 2011 Return-Path: Delivered-To: arch@freebsd.org Received: from mx1.freebsd.org (mx1.freebsd.org [IPv6:2001:4f8:fff6::34]) by hub.freebsd.org (Postfix) with ESMTP id 8633F106564A for ; Sun, 20 Mar 2011 01:19:46 +0000 (UTC) (envelope-from nparhar@gmail.com) Received: from mail-fx0-f54.google.com (mail-fx0-f54.google.com [209.85.161.54]) by mx1.freebsd.org (Postfix) with ESMTP id 1B04F8FC12 for ; Sun, 20 Mar 2011 01:19:45 +0000 (UTC) Received: by fxm11 with SMTP id 11so5453759fxm.13 for ; Sat, 19 Mar 2011 18:19:45 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=gmail.com; s=gamma; h=domainkey-signature:mime-version:in-reply-to:references:date :message-id:subject:from:to:cc:content-type :content-transfer-encoding; bh=SpBQYfmeBYrw/6Zs0uCZRUpG6nkknor/q4sJzqV/c/w=; b=Mo1MxLcMfO/NUAXxvwuxfIkNQRqzTHXi73WwEUxnJrleG6QMp77Y9ReA5mIBc3znim kZoWEQOPY4PaWuhsBC6StomAVo+/kUFSS/3z7BjUxbJlrmcMb4MtUrRB+pQKfzSgLXDk 4jGpHQNkiO6tgKRQFt0/YGrh1Ds4vWAVAst5c= DomainKey-Signature: a=rsa-sha1; c=nofws; d=gmail.com; s=gamma; h=mime-version:in-reply-to:references:date:message-id:subject:from:to :cc:content-type:content-transfer-encoding; b=xJroWfQQBXs2jIGwzVfIvVJZvsNjwT4QZUEqKYD4W//pn/Ik3w1/mAJS9Arj7p93tz XsKSkx2THjhbfBdENOp4WVfYv8QAtZLmlweJWvJL6C9ECoan5FSGNsR+B2LXGrWv5uK+ 1HcoGsb/TakxXN2Kvqgq/LOFjLHzRuCTG/W7g= MIME-Version: 1.0 Received: by 10.223.77.19 with SMTP id e19mr3100914fak.36.1300583985172; Sat, 19 Mar 2011 18:19:45 -0700 (PDT) Received: by 10.223.32.204 with HTTP; Sat, 19 Mar 2011 18:19:45 -0700 (PDT) In-Reply-To: References: <132388F1-44D9-45C9-AE05-1799A7A2DCD9@neville-neil.com> Date: Sat, 19 Mar 2011 18:19:45 -0700 Message-ID: From: Navdeep Parhar To: Gordon Tetlow Content-Type: text/plain; charset=ISO-8859-1 Content-Transfer-Encoding: quoted-printable Cc: arch@freebsd.org, George Neville-Neil Subject: Re: Updating our TCP and socket sysctl values... X-BeenThere: freebsd-arch@freebsd.org X-Mailman-Version: 2.1.5 Precedence: list List-Id: Discussion related to FreeBSD architecture List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , X-List-Received-Date: Sun, 20 Mar 2011 01:19:46 -0000 On Sat, Mar 19, 2011 at 5:38 PM, Gordon Tetlow wrote: > On Sat, Mar 19, 2011 at 4:13 PM, Navdeep Parhar wrote= : >> 256KB seems adequate for 10G (as long as the consumer can keep >> draining the socket rcv buffer fast enough). =A0If you consider 2 x >> bandwidth delay product to be a reasonable socket buffer size then >> 256K allows for 10G networks with ~100ms delays. =A0Normally the delay >> is _way_ less than this for 10G and even 256K may be an overkill (but >> this is ok, the kernel has tcp_do_autorcvbuf on by default) > > The BDP for a 10Gbps link with 100ms delay is about 120MB. I meant 100us (microseconds), sorry. My point still stands - 10G networks have much less one way delay than this. The worst I can find in the lab right now has around ~30us delay. A socket rcv bufsize of 64K maxes out the link in some casual testing with netperf (with autosizing disabled). 256K is already more than what's needed. Regards, Navdeep > > Here's a decent calculator for figuring it out: > http://www.speedguide.net/bdp.php > > Regards, > Gordon >