From owner-freebsd-arch@FreeBSD.ORG Tue Jan 4 01:06:03 2005 Return-Path: Delivered-To: freebsd-arch@freebsd.org Received: from mx1.FreeBSD.org (mx1.freebsd.org [216.136.204.125]) by hub.freebsd.org (Postfix) with ESMTP id 2B28D16A4CE for ; Tue, 4 Jan 2005 01:06:03 +0000 (GMT) Received: from schlepper.zs64.net (schlepper.zs64.net [212.12.50.230]) by mx1.FreeBSD.org (Postfix) with ESMTP id 09FBF43D1F for ; Tue, 4 Jan 2005 01:06:02 +0000 (GMT) (envelope-from stb@lassitu.de) Received: from [IPv6:::1] (schlepper [212.12.50.230]) by schlepper.zs64.net (8.13.1/8.11.1) with ESMTP id j0415vQF029797; Tue, 4 Jan 2005 02:05:59 +0100 (CET) (envelope-from stb@lassitu.de) In-Reply-To: <12394E9FCB7C8441BB238D7F67B402E407E5C6@exch2.verniernetworks.com> References: <12394E9FCB7C8441BB238D7F67B402E407E5C6@exch2.verniernetworks.com> Mime-Version: 1.0 (Apple Message framework v619) Content-Type: text/plain; charset=US-ASCII; format=flowed Message-Id: Content-Transfer-Encoding: 7bit From: Stefan Bethke Date: Tue, 4 Jan 2005 02:05:56 +0100 To: "Youlin Feng" X-Mailer: Apple Mail (2.619) cc: freebsd-arch@freebsd.org Subject: Re: User process starvation in FreeBSD 5.3 X-BeenThere: freebsd-arch@freebsd.org X-Mailman-Version: 2.1.1 Precedence: list List-Id: Discussion related to FreeBSD architecture List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , X-List-Received-Date: Tue, 04 Jan 2005 01:06:03 -0000 Am 03.01.2005 um 23:23 schrieb Youlin Feng: > We are building a network appliance running FreeBSD 5.3 and under very > heavy network traffic the user processes don't get scheduled for an > unacceptable period of time. Marking the user process/thread real-time > class doesn't help since the real-time user threads priorities are > still > lower than the interrupt threads. The effect you're describing very much sounds like 'livelock': the system is so overwhelmed with interrupts that it has no time to do anything else but servicing them. FreeBSD offers polling(4), which is intended to mitigate the overhead of a high interrupt rate on certain network controllers; especially in high-throughput scenarios, it can improve system load, throughput, and latency quite dramatically. On the other hand, your hardware might just not be able handle the packet rate. I'd suggest asking this on freebsd-net, where I believe quite a few people with experience in high-throughput setups are reading. Cheers, Stefan -- Stefan Bethke Fon +49 170 346 0140