[lwip-users] Re: [lwip] lwIP on Gigabit Ethernet

[Adam Dunkels]

Hi!

I agree with what everyone has said about this, and would like to further 
stress the importance of the lwipopts.h settings. The default settings are 
*very* conservative and does not give high performance. 

For high performance, increase the window size (TCP_WND), the TCP maximum 
segment size (TCP_MSS), sender buffer space, turn on queueing of 
out-of-sequence segments, increase PBUF_POOL_SIZE and set PBUF_POOL_BUFSIZE 
to TCP_MSS. Also increase the heap size (MEM_SIZE), the number of avaliable 
TCP segments (MEM_SEG) and the number of pbufs (MEM_PBUF). 

Your TCP window is very small (1024 bytes) so performance probably is limited 
by that. Increase it to 32768 to get things going really fast.

You should also try to rewrite the checksum loop in assembler - that probably 
further increases performance. But I guess that the problem has more to do 
with window sizes and not raw CPU cycles performance in this case.

/adam

On Wednesday 26 June 2002 23.54, you wrote:
> Just putting some information out there..
>
> I have a simple lwIP (0.5.3) echo application running on a gigabit
> Ethernet network - no OS, no sockets API, just the raw lwIP API.  The
> performance is much less than I thought it would be (~4Mb/sec).  Does
> anyone have any comments/suggestions or "I told you so" about this?
>
> The system that its running on is PPC405 @ 200Mhz with an on chip
> Ethernet MAC (one of our own).  The bare metal performance of the system
> (no tcp stack) is about 40Mb/sec - the MAC host interface and driver I
> am working with is not at all optimized (16-bit interface @ 50Mhz, no
> DMA, no interrupts...).  But adding lwIP drops the performance by 10x
> (from 40 downto 4).  That doesn't seem right...
>
> I took a look at the TCP stream.  It looks like host PC fills the window
> (1024) of the lwIP device, and then the connection is reduced to sending
> very very small tcp segments back and forth.
>
> Has anyone else seen similar issues?  I get similar performance on a
> 100Mb/sec line (~4Kb/sec data rate).
>
> Does anyone have any lwIP performance numbers for their applications???
>
>  -Chris
>
> [This message was sent through the lwip discussion list.]

-- 
Adam Dunkels <address@hidden>
http://www.sics.se/~adam
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