From owner-freebsd-net@FreeBSD.ORG Mon Sep 13 22:50:22 2010 Return-Path: Delivered-To: freebsd-net@freebsd.org Received: from mx1.freebsd.org (mx1.freebsd.org [IPv6:2001:4f8:fff6::34]) by hub.freebsd.org (Postfix) with ESMTP id 2AE821065695; Mon, 13 Sep 2010 22:50:22 +0000 (UTC) (envelope-from pyunyh@gmail.com) Received: from mail-gw0-f54.google.com (mail-gw0-f54.google.com [74.125.83.54]) by mx1.freebsd.org (Postfix) with ESMTP id 8E0E48FC17; Mon, 13 Sep 2010 22:50:21 +0000 (UTC) Received: by gwb15 with SMTP id 15so2235393gwb.13 for ; Mon, 13 Sep 2010 15:50:20 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=gmail.com; s=gamma; h=domainkey-signature:received:received:received:from:date:to:cc :subject:message-id:reply-to:references:mime-version:content-type :content-disposition:in-reply-to:user-agent; bh=FsJFlIvxRlQs6Z/I+Imkzs7xTKaKhS4X83HBizlPGvM=; b=nYUlDmnrV5UqPMN/U85zN2R+uXrOTov6X3hDtkF579IHHDERbrC+g+/x5WBTHLNbW+ NhimHdUkwuY/HFubEADNNyqApWHLxXTpW0F4FICI340c/bahKyBzRAtn5hCCMbUZJ37j bmQXaDCeTXMEQiwXHFZbqu3GDT6M7TYDgZ3fc= DomainKey-Signature: a=rsa-sha1; c=nofws; d=gmail.com; s=gamma; h=from:date:to:cc:subject:message-id:reply-to:references:mime-version :content-type:content-disposition:in-reply-to:user-agent; b=mhpUrbggPOCwQd+/olwQlaDDnWmiWnixFp5G/DH0teT/9S/AxNRdf2if6FAt0fGVp/ Unmjm/o/oTeFPPOuVr5r9dIzpsx2mxUar4JTNYYw5puYVhO7mwtqoXP7sAHgrwpgpkum 7/FwKL3CUQtyZ7tEWCFyjkaLDjk0bAw4q4VTs= Received: by 10.101.165.35 with SMTP id s35mr5098703ano.258.1284418220642; Mon, 13 Sep 2010 15:50:20 -0700 (PDT) Received: from pyunyh@gmail.com ([174.35.1.224]) by mx.google.com with ESMTPS id q7sm10837809anf.26.2010.09.13.15.50.17 (version=TLSv1/SSLv3 cipher=RC4-MD5); Mon, 13 Sep 2010 15:50:19 -0700 (PDT) Received: by pyunyh@gmail.com (sSMTP sendmail emulation); Mon, 13 Sep 2010 15:49:25 -0700 From: Pyun YongHyeon Date: Mon, 13 Sep 2010 15:49:25 -0700 To: David Christensen Message-ID: <20100913224925.GK1229@michelle.cdnetworks.com> References: <4C894A76.5040200@tomjudge.com> <20100910002439.GO7203@michelle.cdnetworks.com> <4C8E3D79.6090102@tomjudge.com> <20100913184833.GF1229@michelle.cdnetworks.com> <4C8E775D.8070202@freebsd.org> <20100913193947.GH1229@michelle.cdnetworks.com> <5D267A3F22FD854F8F48B3D2B52381933B540B4C14@IRVEXCHCCR01.corp.ad.broadcom.com> Mime-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <5D267A3F22FD854F8F48B3D2B52381933B540B4C14@IRVEXCHCCR01.corp.ad.broadcom.com> User-Agent: Mutt/1.4.2.3i Cc: Tom Judge , "freebsd-net@freebsd.org" , Andre Oppermann , "yongari@freebsd.org" Subject: Re: bce(4) - com_no_buffers (Again) X-BeenThere: freebsd-net@freebsd.org X-Mailman-Version: 2.1.5 Precedence: list Reply-To: pyunyh@gmail.com List-Id: Networking and TCP/IP with FreeBSD List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , X-List-Received-Date: Mon, 13 Sep 2010 22:50:22 -0000 On Mon, Sep 13, 2010 at 03:21:13PM -0700, David Christensen wrote: > > I'm under the impression the header splitting in bce(4) is for > > LRO(opposite of TSO), not for VM magic to enable page flipping > > tricks. > > Header splitting was implemented in the Linux version of bce(4) > to prevent jumbo memory allocations. Allocating 9KB frames was > causing problems on systems used for virtualization. (Harder to > find a contiguous 9KB frame when a hypervisor is in use.) Using > 4KB or smaller buffer sizes was considered more compatible with > virtualization. > > LRO (Large Receive Offload, aka Transparent Packet Aggregation > or TPA on the 10Gb controllers) is not supported on the 1Gb > bce(4) devices. > I meant tcp_lro implementation of FreeBSD. ATM tcp_lro_rx() runs long list of sanity checks before combining TCP segments into a TCP segment but if TCP header is split with its payload I guess we can optimize that path. This way we may be able to support LRO over VLAN, I guess.