From owner-freebsd-net@FreeBSD.ORG Thu Nov 28 12:57:26 2013 Return-Path: Delivered-To: freebsd-net@freebsd.org Received: from mx1.freebsd.org (mx1.freebsd.org [IPv6:2001:1900:2254:206a::19:1]) (using TLSv1 with cipher ADH-AES256-SHA (256/256 bits)) (No client certificate requested) by hub.freebsd.org (Postfix) with ESMTPS id D56479DB for ; Thu, 28 Nov 2013 12:57:26 +0000 (UTC) Received: from mzh.zlo.nu (ns0.zlo.nu [85.17.141.90]) by mx1.freebsd.org (Postfix) with ESMTP id 9ECB11C64 for ; Thu, 28 Nov 2013 12:57:25 +0000 (UTC) Received: by mzh.zlo.nu (Postfix, from userid 1000) id C5442140CB; Thu, 28 Nov 2013 13:49:44 +0100 (CET) Date: Thu, 28 Nov 2013 13:49:44 +0100 From: Marc Olzheim To: Meny Yossefi Subject: Re: UDP traffic, msg size exceeds 9215 Bytes Message-ID: <20131128124944.GA15691@zlo.nu> References: MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: User-Agent: Mutt/1.5.20 (2009-06-14) Cc: "freebsd-net@freebsd.org" , Oded Shanoon X-BeenThere: freebsd-net@freebsd.org X-Mailman-Version: 2.1.16 Precedence: list List-Id: Networking and TCP/IP with FreeBSD List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , X-List-Received-Date: Thu, 28 Nov 2013 12:57:26 -0000 On Thu, Nov 28, 2013 at 12:43:43PM +0000, Meny Yossefi wrote: > Hi all, > > We've been running some benchmarks (Netperf, Iperf) on our driver (Mellanox), and witnessed an odd behavior. > We saw that when running UDP traffic with msg size larger than 9215 bytes, it gets dropped for some reason. MTU is 1500. > > We've spotted the same behavior on different vendors which lead us to believe there's some kernel issue that we are missing here. Did you meddle with sysctl net.inet.udp.maxdgram yet ? The default value is 6 * 1536 = 9216 bytes... Marc