Re: [lwip-users] TCP bandwidth limited by rate of ACKs

[Bill Auerbach]

>-----Original Message-----
>I was expecting to reach 80+ Mbit/s, so I captured the conversation
>with Wireshark, and I noticed that the sender is being throttled
>because the receiver (the STB running lwip) is not sending ACKs
>fast enough.
>
>cf. STB_TCP_RX_2.pcap (6 MB -- I truncated payloads to 100 bytes)
>http://dl.free.fr/tKDBuYTrc
>
>(I've also attached a copy of my current lwipopts.h)
>
>Can someone nudge me in the right direction to optimize my
>build of lwip?

Some things are to optimize are the internet checksum, use zero-copy receive
and transmit, do SMEMCPY more efficiently, review/optimize memcpy, and use
RAW API.

Use LWIP_CHKSUM_ALGORITHM = 3 as it looks like it might be the best choice
for your processor.  Or better, code the checksum in assembly language.

If you can't use zero-copy receive and you have to copy the data, use a DMA
memory-to-memory copy if your hardware supports it.  The less you touch the
data the better.

Everything else I've done has been hardware dependent or used FPGA resources
(e.g. internet checksum).

Bill