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Re: [lwip-users] TCP bandwidth limited by rate of ACKs
From: |
Mason |
Subject: |
Re: [lwip-users] TCP bandwidth limited by rate of ACKs |
Date: |
Tue, 11 Oct 2011 17:02:56 +0200 |
User-agent: |
Mozilla/5.0 (Windows NT 5.1; rv:7.0.1) Gecko/20110928 Firefox/7.0.1 SeaMonkey/2.4.1 |
Bill Auerbach wrote:
> Mason wrote:
>
>> 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
>>
>> Can someone nudge me in the right direction to optimize my
>> build of lwip?
>
> Some things are to optimize are the internet checksum,
As a first-order approximation, I simply disabled CHECKSUM_CHECK_TCP.
I don't think the IPv4 checksum check (20 bytes) has much of an impact
on performance, do you?
> use zero-copy receive and transmit,
I wish I could, but I've no idea how to accomplish that.
cf. my previous thread "Custom memory management"
http://lists.gnu.org/archive/html/lwip-users/2011-10/msg00008.html
> do SMEMCPY more efficiently,
I'm not sure I can do it better than my platform's memcpy.
> review/optimize memcpy,
I will try profiling to see if we're indeed spending most of
the time copying data.
> and use RAW API.
I can't. I need to implement the BSD sockets 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).
Thanks for the suggestions, I'll try some of them.
--
Regards.
- Re: [lwip-users] TCP bandwidth limited by rate of ACKs, (continued)
- Re: [lwip-users] TCP bandwidth limited by rate of ACKs, Bill Auerbach, 2011/10/12
- Re: [lwip-users] TCP bandwidth limited by rate of ACKs, Mason, 2011/10/12
- Re: [lwip-users] TCP bandwidth limited by rate of ACKs, address@hidden, 2011/10/12
- Re: [lwip-users] TCP bandwidth limited by rate of ACKs, Mason, 2011/10/13
- Re: [lwip-users] TCP bandwidth limited by rate of ACKs, address@hidden, 2011/10/13
- Re: [lwip-users] TCP bandwidth limited by rate of ACKs, Mason, 2011/10/17
- Re: [lwip-users] TCP bandwidth limited by rate of ACKs, address@hidden, 2011/10/17
- Re: [lwip-users] TCP bandwidth limited by rate of ACKs, Mason, 2011/10/18
- Re: [lwip-users] TCP bandwidth limited by rate of ACKs, Simon Goldschmidt, 2011/10/18
Re: [lwip-users] TCP bandwidth limited by rate of ACKs, Bill Auerbach, 2011/10/10
- Re: [lwip-users] TCP bandwidth limited by rate of ACKs,
Mason <=