From owner-freebsd-current@FreeBSD.ORG Thu Sep 18 15:27:48 2014 Return-Path: Delivered-To: freebsd-current@freebsd.org Received: from mx1.freebsd.org (mx1.freebsd.org [8.8.178.115]) (using TLSv1 with cipher ADH-AES256-SHA (256/256 bits)) (No client certificate requested) by hub.freebsd.org (Postfix) with ESMTPS id 29AF93B0; Thu, 18 Sep 2014 15:27:48 +0000 (UTC) Received: from mail-pd0-x22c.google.com (mail-pd0-x22c.google.com [IPv6:2607:f8b0:400e:c02::22c]) (using TLSv1 with cipher ECDHE-RSA-RC4-SHA (128/128 bits)) (Client CN "smtp.gmail.com", Issuer "Google Internet Authority G2" (verified OK)) by mx1.freebsd.org (Postfix) with ESMTPS id E42677E2; Thu, 18 Sep 2014 15:27:47 +0000 (UTC) Received: by mail-pd0-f172.google.com with SMTP id v10so1624243pde.17 for ; Thu, 18 Sep 2014 08:27:47 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=gmail.com; s=20120113; h=mime-version:in-reply-to:references:date:message-id:subject:from:to :cc:content-type; bh=PwOOEuTXCiU40DQ0+jIMK2m+x87Q8Pn4FYuUJkOHEQM=; b=CaWeokpPaew6TbzagIWIgZTj+1zlqYItN0V6kG5z9BFFhSaSGc9bh7kQyviY+/Tyj7 nfzOls9SPeu3uSdOz7bpQk8ZLkOtYgi9WyxnViQgJYOQOiWGVT7p2yCyISBcKwGgNHHO UKQ6OtJaAO9waa3uGCJyvma+be2NzyvZ2mAXYCxoESqcSt5+T78VnbUwBXzfuZXNntrH FnoHwbkFhWLDXKEaPeNGSAmscQFNbBl3z5HxY03g5CPFDRAMVtSeZ5xMCatmwjYDtnqp o5zD1BfgrFFgioD6HSUsudS7eEozf2SpcuYtS/egkFiTt7SbxM3lswq/GAUD1HV0xedH OwCw== MIME-Version: 1.0 X-Received: by 10.70.42.7 with SMTP id j7mr6284590pdl.9.1411054067133; Thu, 18 Sep 2014 08:27:47 -0700 (PDT) Received: by 10.202.104.89 with HTTP; Thu, 18 Sep 2014 08:27:47 -0700 (PDT) In-Reply-To: References: <5419EE95.40600@selasky.org> Date: Thu, 18 Sep 2014 08:27:47 -0700 Message-ID: Subject: Re: [RFC] Patch to add Software/Generic Segmentation Offload (GSO) support in FreeBSD From: Freddie Cash To: Stefano Garzarella Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: quoted-printable X-Content-Filtered-By: Mailman/MimeDel 2.1.18-1 Cc: Hans Petter Selasky , Adrian Chadd , "freebsd-net@freebsd.org" , George Neville-Neil , freebsd-current , Luigi Rizzo X-BeenThere: freebsd-current@freebsd.org X-Mailman-Version: 2.1.18-1 Precedence: list List-Id: Discussions about the use of FreeBSD-current List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , X-List-Received-Date: Thu, 18 Sep 2014 15:27:48 -0000 On Thu, Sep 18, 2014 at 7:16 AM, Stefano Garzarella < stefanogarzarella@gmail.com> wrote: > I saw the discussion about TSO, but the GSO is a software > implementation unrelated with the hardware. > Furthermore, if the TSO is enabled (and supported by the NIC), the GSO is > not executed, because is useless. > > After the execution of the GSO, the packets, that are passed to the devic= e > driver, are smaller (or equal) than MTU, so the TSO is unnecessary. For > this reason the GSO doesn't look neither "ifp->if_hw_tsomax" nor hardware > segment limits. > > The GSO is very useful when you can't use the TSO. > =E2=80=8BHow does GSO affect IPFW, specifically the libalias(3)-based, in-k= ernel NAT? The ipfw(8) man page mentions that it doesn't play nicely with hardware-based TSO, and that one should disable TSO when using IPFW NAT. Will the software-based GSO play nicely with IPFW NAT?=E2=80=8B Will it ma= ke any difference to packet throughput through IPFW? Or is it still way too early in development to be worrying about such things? :) --=20 Freddie Cash fjwcash@gmail.com