[lwip-users] very poor performance of httpd

[Felix Frey]

Hi,

I've running an application on a STM32F429 using LwIP 2.0.3 and it's httpd.
Basically it works fine, however the performance of the httpd is very poor.

When the browser does a http request for a total of five files (statically 
linked)
with a total amount of 40kB, it takes about 5sec to complete the request. 
It seems like the httpd gets stalled.
In the log I can see several of the entrys below:
-----
00006.560: http_poll: pcb=0x2000d7b8 hs=0x2000db08 pcb_state=ESTABLISHED        
                                      
00006.560: http_poll: try to send more data                                     
                                      
00006.560: http_send: hs=0x2000db08 pcb=0x2000d7b8 left=22030                   
                                      
00006.560: Trying to send 0 bytes                                               
                                      
00006.560: Sent 0 bytes                                                         
                                      
00006.560: send_data end.                                                       
                                      
00006.560: tcp_output
-----
This is repeated every 500ms for about 2sec until sending moves on.
It looks like it simply doesn't anything during this time. Why??

My memory settings are:
#define MEM_LIBC_MALLOC 1
#define MEMP_NUM_TCP_PCB 8
#define MEMP_NUM_PBUF 32
#define TCP_MSS 1460
#define TCP_WND 2920

I've already played with configuration settings, however, it didn't change a 
lot.
Can anybody explain this behaviour or even help to improve it?

Thanks in advance.
Felix