[lwip-users] calculating memory #define(s) in lwip

[Bandu]

Hi,

 

I'm having problem setting a proper values for the following #defines

 

#define MEM_SIZE                        (24 * 1024) 

 

#define MEMP_NUM_PBUF                   16
#define MEMP_NUM_TCP_PCB              8       

#define MEMP_NUM_TCP_SEG              16     

#define PBUF_POOL_SIZE                     16

#define TCP_WND                                 (8 * 1024)  

#define TCP_MSS                                1024       
#define TCP_SND_BUF                         (8 * TCP_MSS)

#define TCP_SND_QUEUELEN               (MEMP_NUM_TCP_SEG) *4

#define PBUF_LINK_HLEN                    16

#define PBUF_POOL_BUFSIZE             256

Which of the above are related to TCP Tx and which are Rx?

 

How do I calculate those values to get an optimum throughput ?

 

I'm using Luminary Micro LM3S6965 which got 64KB RAM. and I'm opening 2 TCP port transfering data to PC.

 

PC <-------> MCU with lwIP 1.3 (2 TCP channel transfering data from 2xUART using 230Kbps).

 

When I open only 1 TCP port and transfer the data, the transmission is fast and smooth.

The problem is,  when 2 TCP port are opened and device is connected to 10Mbps Hub both data transfer starting to slow down significantly and i can see the data transfer are starting and stopping.

 

In my firmware, I got sometimes a) snd_queuelen was fulled on one of the port  b) i got ERR_MEM on tcp_write most of the time c) snd_buf size become 0 or very low and never free up again.

I'm sure my ethernet driver is NOT in promicuous mode.

 

Am I setting those #define completely wrong?

 

It would be great if you guys can give me suggestion or thoughts about what would causing me the issue.

 

Thank you very much.

 

--
Bandu
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