Re: [lwip-users] ERR_MEM when sending large data, LWIP stats show no error

[Adrian Figueroa]

It seems like I do not have this problem if I choose TCP_SND_BUF to be exactly double the TCP_MSS of 1460. If I choose higher values, the problem happens.

 

Is there an explanation for this?

 

Von: lwip-users [mailto:lwip-users-bounces+address@hidden Im Auftrag von Adrian Figueroa
Gesendet: Friday, September 1, 2017 10:16 AM
An: address@hidden
Betreff: [lwip-users] ERR_MEM when sending large data, LWIP stats show no error

 

Hello all,

 

I am trying to send large amounts of data continuously. I use lwIP as a TCP client on an STM32F7 and Matlab on a PC as a TCP server.

 

I send blocks of 32768 bytes. Here are some settings for the memory sizes in lwIP:

 

#define MEM_ALIGNMENT 4

#define MEM_SIZE 17520

#define MEMP_NUM_TCP_SEG 65

#define PBUF_POOL_BUFSIZE 1516

#define TCP_WND 8760

#define TCP_MSS 1460

#define TCP_SND_BUF 8760

 

When sending with tcp_write(), I get ERR_MEM errors. So, I switched on LWIP_STATS for seeing memory statistics. When should I be using tcp_output()? Should I check for the remaining tcp_sndbuf and use tcp_output() if it gets low?

 

In Wireshark, I can see TCP Dup ACKs and “TCP Previous segment not captured” errors. Find the dump here:

 

https://sync.coda.pw/r/Z_uuIXRtl2#NT5OwZOSW4Nd8erfCRvLvSdAmMS1YODnWL3tP+dGRMk=

 

I send data every 2 seconds and it takes around 1.5 seconds to send it to the PC, which is too long.

 

Here are some of the results after ERR_MEM happened:

https://snip.coda.pw/?69c4627d150293fa#3cUX2gAqvAKaflXk8NTs7k+TxBAjQwmNT+IYu+GfiJE=

 

There is no Mem/Memp section that contains even one error. So, I am not sure where to look next.

 

Thank you in advance!

Adrian