From owner-freebsd-net@FreeBSD.ORG Wed Feb 15 09:12:42 2006 Return-Path: X-Original-To: net@freebsd.org Delivered-To: freebsd-net@FreeBSD.ORG Received: from mx1.FreeBSD.org (mx1.freebsd.org [216.136.204.125]) by hub.freebsd.org (Postfix) with ESMTP id 65F1616A420 for ; Wed, 15 Feb 2006 09:12:42 +0000 (GMT) (envelope-from raglon@packetfront.com) Received: from mail.packetfront.com (mail.packetfront.com [212.247.6.198]) by mx1.FreeBSD.org (Postfix) with ESMTP id E7C5D43D45 for ; Wed, 15 Feb 2006 09:12:41 +0000 (GMT) (envelope-from raglon@packetfront.com) Received: from localhost (localhost [127.0.0.1]) by mail.packetfront.com (Postfix) with ESMTP id 52B2EA3436; Wed, 15 Feb 2006 10:12:42 +0100 (CET) Received: from mail.packetfront.com ([127.0.0.1]) by localhost (mail.packetfront.com [127.0.0.1]) (amavisd-new, port 10024) with ESMTP id 00961-03; Wed, 15 Feb 2006 10:12:42 +0100 (CET) Received: from [192.168.1.137] (unknown [192.168.1.137]) by mail.packetfront.com (Postfix) with ESMTP id 0DEC1A3425; Wed, 15 Feb 2006 10:12:42 +0100 (CET) Message-ID: <43F2F03D.90603@packetfront.com> Date: Wed, 15 Feb 2006 10:11:25 +0100 From: Ragnar Lonn User-Agent: Mozilla Thunderbird 0.8 (Windows/20040913) X-Accept-Language: en-us, en MIME-Version: 1.0 To: Ivan Voras References: <43F0CE40.5040800@fer.hr> <43F1A2D1.7040402@packetfront.com> <43F24E7E.4060503@fer.hr> In-Reply-To: <43F24E7E.4060503@fer.hr> Content-Type: text/plain; charset=ISO-8859-2; format=flowed Content-Transfer-Encoding: 7bit X-Virus-Scanned: by amavisd-new-20030616-p10 (Debian) at packetfront.com Cc: net@freebsd.org Subject: Re: TCP Performance advice needed [long!] X-BeenThere: freebsd-net@freebsd.org X-Mailman-Version: 2.1.5 Precedence: list List-Id: Networking and TCP/IP with FreeBSD List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , X-List-Received-Date: Wed, 15 Feb 2006 09:12:42 -0000 Ivan Voras wrote: > I understand this bottleneck, and know (at least in theory :) ) how it > could be solved, but my problems are not directly related to that: > > - For small (but consistent in size) packet sizes, I get randomly > varying round-trip times, and much lower packets-per-second ratio then > with big packets (consistent in size) with the exact same lock-step > protocol. Packet generation and processing are not CPU intensive. > > - When using big packets (actually, when switching back and forth from > small packets to big packets), the PPS performance starts low and > climbs to "normal" levels, and I'd like to avoid this. This is a local > network with 0 errors. My guess would be that it's an effect of how TCP works. The slow start, for instance (but I saw you had tried setting TCP_NODELAY). Maybe you should experiement with UDP as the transport protocol instead. Of course, it requires more work if you need reliable and in-order delivery. But if you want low roundtrip times, use UDP. There isn't an online action game today that uses TCP, because it's not suited for applications which need fast response times. Cheers, /Ragnar