netdev - Re: TCP communication for raw image transmission

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Message-ID: <CAL8zT=gbCmtNpw1Lot0P7zB+b_Kw911jhxsXCzO3JOBmMLRcFg@mail.gmail.com>
Date:	Mon, 2 Jan 2012 17:40:54 +0100
From:	Jean-Michel Hautbois <jhautbois@...il.com>
To:	Eric Dumazet <eric.dumazet@...il.com>
Cc:	netdev@...r.kernel.org
Subject: Re: TCP communication for raw image transmission

>> I don't really know what it can do, but it has to do encoding (even if
>> it is a SoC, with dedicated devices, memory has to be used).
>> The main problem I have, is that I don't have the two boards with me
>> today, and even if I can prototype on x86, I can't conclude as far as
>> I don't test on the real HW.
>
> Thats going to be tough. You could at least use one board and test if it
> can send 100Mbits using netperf (on a x86 target), and check cpu usage.

Mmmh, using netperf you would like to know what the client (my ARM
board) can do ?
How would you test it ? I can have an ARM board on one side, and the
x86 on the other...

>> This is also why I want to prototype my best bet in the first try :).
>> And this is mainly a networking/memory problem.
>
> If the 'no packet loss happens in the network' requirement is OK, then a
> plain sendfile() [ or splice() ] will work.
>
> Limiting each tcp frame to a 1 or 2 lines of your image is about
> limiting MSS on your tcp session (setsockopt( ... TCP_MAXSEG ))

Yes, the idea of limiting tcp frame to 2 lines is to avoid
fragmenting. So, with a MTU at 1500, MSS=1460, I can put 2 lines <=
730bytes. I will probably have ~700bytes.

JM
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