Date: Thu, 18 Sep 2014 08:27:47 -0700 From: Freddie Cash <fjwcash@gmail.com> To: Stefano Garzarella <stefanogarzarella@gmail.com> Cc: Hans Petter Selasky <hps@selasky.org>, Adrian Chadd <adrian@freebsd.org>, "freebsd-net@freebsd.org" <freebsd-net@freebsd.org>, George Neville-Neil <gnn@neville-neil.com>, freebsd-current <freebsd-current@freebsd.org>, Luigi Rizzo <rizzo@iet.unipi.it> Subject: Re: [RFC] Patch to add Software/Generic Segmentation Offload (GSO) support in FreeBSD Message-ID: <CAOjFWZ73X=v6=KgeF%2BTpRCAe=KbXm1Yp3iKpKDeqyKK12Ejtwg@mail.gmail.com> In-Reply-To: <CAO0mX5ZGGY5fMmc%2BTFrknFrGrErrB7fx=f%2BSDMRg7oTTVHTRVg@mail.gmail.com> References: <CAO0mX5bDoCe8oRNmd%2BUBbr4bJcgQEzhAQKyTsyxEQciyvGTdgQ@mail.gmail.com> <CAJ-VmomY7M2h2Bbuu5BXRUYFRMnKXezZfCNbNWGFHACuFwNDmg@mail.gmail.com> <CAO0mX5Zdt487=entnjrMjxpt%2BLhKTNkS=sUHsnyVDYr_PXyS7Q@mail.gmail.com> <5419EE95.40600@selasky.org> <CAO0mX5ZGGY5fMmc%2BTFrknFrGrErrB7fx=f%2BSDMRg7oTTVHTRVg@mail.gmail.com>
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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
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