From owner-freebsd-stable@FreeBSD.ORG Thu Oct 12 22:24:28 2006 Return-Path: X-Original-To: freebsd-stable@freebsd.org Delivered-To: freebsd-stable@freebsd.org Received: from mx1.FreeBSD.org (mx1.freebsd.org [216.136.204.125]) by hub.freebsd.org (Postfix) with ESMTP id 5067916A407 for ; Thu, 12 Oct 2006 22:24:28 +0000 (UTC) (envelope-from cswiger@mac.com) Received: from smtpout.mac.com (smtpout.mac.com [17.250.248.184]) by mx1.FreeBSD.org (Postfix) with ESMTP id 0A3F143D5F for ; Thu, 12 Oct 2006 22:24:28 +0000 (GMT) (envelope-from cswiger@mac.com) Received: from mac.com (smtpin05-en2 [10.13.10.150]) by smtpout.mac.com (Xserve/8.12.11/smtpout14/MantshX 4.0) with ESMTP id k9CMORqN009902; Thu, 12 Oct 2006 15:24:27 -0700 (PDT) Received: from [17.214.13.96] (a17-214-13-96.apple.com [17.214.13.96]) (authenticated bits=0) by mac.com (Xserve/smtpin05/MantshX 4.0) with ESMTP id k9CMOQ2Y024263; Thu, 12 Oct 2006 15:24:26 -0700 (PDT) In-Reply-To: References: Mime-Version: 1.0 (Apple Message framework v752.2) Content-Type: text/plain; charset=US-ASCII; delsp=yes; format=flowed Message-Id: Content-Transfer-Encoding: 7bit From: Chuck Swiger Date: Thu, 12 Oct 2006 15:24:25 -0700 To: Scott Ullrich X-Mailer: Apple Mail (2.752.2) X-Brightmail-Tracker: AAAAAA== X-Brightmail-scanned: yes Cc: freebsd-stable Subject: Re: Userland freezes during heavy packet forwarding workloads X-BeenThere: freebsd-stable@freebsd.org X-Mailman-Version: 2.1.5 Precedence: list List-Id: Production branch of FreeBSD source code List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , X-List-Received-Date: Thu, 12 Oct 2006 22:24:28 -0000 On Oct 12, 2006, at 2:11 PM, Scott Ullrich wrote: > We (pfSense developers) have noticed an interesting problem where > userland stops functioning under high packet forwarding workloads. > Userland applications such as sshd and lighttpd freeze but userland > resumes after the network load eases. [ ...note that the links you posted included the trailing square bracket, and thus were broken, although easily fixable by hand... ] > Is there anything we can do to prevent userland from stopping > completely when under heavy load? Is this a bug? You're probably experiencing some form of "livelock"; your hardware isn't horribly fast, and if the NICs are generating interrupts rapidly enough due to the high rate of packet forwarding, you're not going to have a lot of spare CPU available to run userland tasks. I notice you're compiling in support for DEVICE_POLLING; does enabling it do anything to help the responsiveness of the userland tasks under high network load? You might try adjusting HZ from 100 to 250 or so...I found that made a decent tradeoff between packet delay and scheduler overhead on similar Soerkis 4801 or VIA C3/EPIA-M hardware to yours. -- -Chuck