From owner-freebsd-questions@FreeBSD.ORG Wed Nov 18 01:19:36 2009 Return-Path: Delivered-To: questions@freebsd.org Received: from mx1.freebsd.org (mx1.freebsd.org [IPv6:2001:4f8:fff6::34]) by hub.freebsd.org (Postfix) with ESMTP id 986D11065670 for ; Wed, 18 Nov 2009 01:19:36 +0000 (UTC) (envelope-from cswiger@mac.com) Received: from asmtpout014.mac.com (asmtpout014.mac.com [17.148.16.89]) by mx1.freebsd.org (Postfix) with ESMTP id 86B998FC08 for ; Wed, 18 Nov 2009 01:19:36 +0000 (UTC) MIME-version: 1.0 Content-transfer-encoding: 7BIT Content-type: text/plain; charset=US-ASCII; format=flowed; delsp=yes Received: from cswiger1.apple.com ([17.227.140.124]) by asmtp014.mac.com (Sun Java(tm) System Messaging Server 6.3-8.01 (built Dec 16 2008; 32bit)) with ESMTPSA id <0KTA00MWI6CNZ030@asmtp014.mac.com> for questions@freebsd.org; Tue, 17 Nov 2009 17:19:36 -0800 (PST) Message-id: From: Chuck Swiger To: Brett Glass In-reply-to: <200911180032.RAA21582@lariat.net> Date: Tue, 17 Nov 2009 17:19:35 -0800 References: <200911180032.RAA21582@lariat.net> X-Mailer: Apple Mail (2.936) Cc: questions@freebsd.org Subject: Re: State of interface polling in FreeBSD X-BeenThere: freebsd-questions@freebsd.org X-Mailman-Version: 2.1.5 Precedence: list List-Id: User questions List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , X-List-Received-Date: Wed, 18 Nov 2009 01:19:36 -0000 Hi-- On Nov 17, 2009, at 4:32 PM, Brett Glass wrote: > I'm building a FreeBSD router based on a small, Intel Atom-based > board and am trying to decide whether or not to configure the kernel > for polling. What's the current state of interface polling in > FreeBSD? Is it worth doing with a single CPU, or will it actually > increase system overhead? What "HZ" settings are recommended? Polling probably works better with a single CPU, compared with doing service handling threads per interface, which can do better on SMP boxes. However, the main consideration is probably whether your NICs know how to do interrupt mitigation-- if they do, using that is probably better than using device polling, at least for low-to- moderate network load. Polling handles high load better; it wastes a fair amount of CPU under no to low network load. The base recommendation is to set HZ to 1000. If your CPU is having problems with that, try 250 or 500 HZ. Regards, -- -Chuck