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 device > 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. > How does GSO affect IPFW, specifically the libalias(3)-based, in-kernel 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? Will it make any difference to packet throughput through IPFW? Or is it still way too early in development to be worrying about such things? :) -- Freddie Cash fjwcash@gmail.com
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