Re: [lwip-users] Performance Tuning?

[David Haas]

Hi David,

I would really recommend you port your code to the latest version of 
lwip. It has many bug fixes and performance improvements.

Take a look at the coldfire version of lwipopts.h in the 
contrib/ports/coldfire area. I tried hard to optimize for some 
performance. I think lwip is quite sensitive to the pbuf size. You want 
to make sure that is a decent size (1024 or bigger).

One other thing you want to watch out for is how you output data via 
TCP. You want to make sure your writes have a relatively large amount of 
data in them. I wrote a telnet server and was using that as a console 
for my application. I was getting terrible performance, but I found out 
that the code was basically calling a putc() routine for every character 
that wound up in a separate tcp frame. No wonder it was so slow. I 
implemented a buffering scheme in my pseudo-terminal layer and it 
improved performance immensely. I have'nt measured real performance 
quantitatively yet. At some point I have to implement an ftp server and 
I will probably do it then.

How are you measuring performance?

Regards,
David.


David Ryan wrote:

> Hi All..
>
> Another question..  I thought I'd keep it seperate from the last post 
> as its on a rather different subject.  Users of our 
> implementation(based on lwip 0.5.3) have been complaining that the 
> performance they get from the stack is around 150kb/sec - 350kb/sec 
> using a 100mbit ethernet adapter. This seems to be way below the 
> theoretical maximum and below the 1.5mb/sec people are getting using 
> ps2linux on the same hardware.
>
> I realise that performance can be effected by many things, however I'd 
> like to know if there is any documentation or experience from people 
> on how best to tune lwipopts.h for better performance when dealing 
> with streaming data.  Obviously some values relate to each other.  The 
> question is which values relate to each other and how..  and how 
> should they be managed to get the best performance.
>
> Thanks,
> David.
>
>
>
>
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