[lwip-users] LWIP Memory options question

[shogun]

LWIP Memory options question

I have been using LWIP on a Stellaris CPU with TI's code Composer Studio and
have had it working for some time but I have some questions about tuning it
for RAM usage.  I have plenty of code space but limited RAM (96K RAM) total.
The application is using LWIP only for three TCP/IP sockets so no UDP etc.
The messages are all 256 bytes in both direction but one socket does send
about 10k bytes of data at about 10 times a second.  For LWIP, I am
currently using memory defined only by MEM_SIZE, so MEM_LIBC_MALLOC,
MEM_USE_POOLS and MEMP_USE_CUSTOM_POOLS all are zero.  My MEM_SIZE is
defined as (15 * 1024).  

I have read the wiki, opt.h file, lwipopts.h and searched through this forum
but I still have a few things that are not clear to me I wanted to see if I
could get some help understanding this.


1)      Would there be benefit in my app of using MEM_LIBC_MALLOC?  I don't
use malloc or free in my application anywhere and I am not concerned with
code space.  Would there be any RAM savings if I were to turn
MEM_LIBC_MALLOC on?   I have seen comments about the risk of fragmentation
if using MEM_LIBC_MALLOC so I don't know if it's with the risk to use
MEM_LIBC_MALLOC.  Could someone explain the risk of fragmentation?
2)       If I did decide to use MEM_LIBC_MALLOC, how much RAM would I need
to tell the compiler to reserve from the heap for lwip?  Based on what I am
using now, would I need to tell the compiler to allow about what I have
defined for (MEM_SIZE) now 15K in my case?

Is there a picture anywhere that shows a "memory map" of how the memory LWIP
uses is broken down into pbufs,  pools etc?

Thanks,


DB