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Date:      Tue, 19 Jan 2016 12:23:04 -0800
From:      Adrian Chadd <adrian.chadd@gmail.com>
To:        Hans Petter Selasky <hps@selasky.org>
Cc:        Ryan Stone <rysto32@gmail.com>,  "src-committers@freebsd.org" <src-committers@freebsd.org>,  "svn-src-all@freebsd.org" <svn-src-all@freebsd.org>,  "svn-src-head@freebsd.org" <svn-src-head@freebsd.org>
Subject:   Re: svn commit: r294327 - in head/sys: dev/cxgb dev/cxgbe dev/e1000 dev/hyperv/netvsc dev/ixgbe dev/mxge netinet sys
Message-ID:  <CAJ-Vmo=vi5fdGzx6Z6%2BD5szrpf0jcaOe7a_9u-o0V7%2B9YkE6qw@mail.gmail.com>
In-Reply-To: <569E9B66.1070200@selasky.org>
References:  <201601191533.u0JFXSxf037804@repo.freebsd.org> <CAFMmRNz3uXim3H3-sGuBUBs45Jy8p260ywothgp4iFkUcnvnEw@mail.gmail.com> <569E6A38.8080108@selasky.org> <CAFMmRNx3zC=mz=TC2Aq5==a5vh0Fqzv1domrCL2uUHnjybZSkQ@mail.gmail.com> <CAJ-Vmoki0yCU-mmPGfrGyJ_ar_=KKkto_ioomo_Ri_HCWR70cg@mail.gmail.com> <569E909B.60506@selasky.org> <CAJ-Vmo=1vTmKnoM=wVX=vv99mnkW-Q2CKkxZUNTUBkw_CU6ahQ@mail.gmail.com> <569E9B66.1070200@selasky.org>

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On 19 January 2016 at 12:24, Hans Petter Selasky <hps@selasky.org> wrote:
> On 01/19/16 21:05, Adrian Chadd wrote:
>>
>> Erm, ok. So I'm confused about the state of how the streams are
>> tracked. So not all mbufs are in a stream, but they're in some single
>> LRO mbuf list?
>>
>
> Hi,
>
> The streams are typically tracked using the hardware generated Toeplitz hash
> value. The mbufs are sorted according to the hash value and the hash type.
> The list of mbufs is scanned, flushing the LRO entries every time we see a
> change in the hash value or hash type. OK?

Sure, but TCP fragments and non-fragments can hash to different
values, so suddenly you get interleaved packets.

You can't rely on the toeplitz hash 100% hashing /all packets in a
stream/ reliably, because it's highly dependent upon the NIC config.

This is why I did all that effort in the RSS code to handle things.

-a



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