[lwip-users] Performance issue: sending large buffers

[Peter]

Hello Vincenzo

Like me you will waste half your life trying to get answers. Almost 
nobody replies on lwip etc issues...

I suggest you post your lwipopts file. Also the ETH buffer settings in 
one of the .h files

uint8_t Tx_Buff[ETH_TXBUFNB][ETH_TX_BUF_SIZE]
uint8_t Rx_Buff[ETH_RXBUFNB][ETH_RX_BUF_SIZE]

And your ethernetif_input() and low_level_input() functions.

I have just spent a few days on this stuff and started with 
100kbytes/sec and now can do 1200kbytes/sec albeit with more RAM for 
buffers, so I traded it off at 250kbytes/sec. I think one could get 
2000kbytes/sec if one didn't have other constraints and had interrupt 
driven RX (168MHz 32F417).

I am also polling in ethernetif_input() which is sub-optimal but works 
ok, and there are lots of other tasks running.

Note that there are many issues which arise if e.g. you want the LWIP 
API thread-safe. You need LWIP_TCPIP_CORE_LOCKING=1 and then you need a 
separate set of mutexes around the low level stuff.

// RTOS task; runs for ever
void ethernetif_input( void * argument )
{
        struct pbuf *p;
        struct netif *netif = (struct netif *) argument;

	// This mutex position is based on an idea from Piranha here, with the 
delay added
	// 
https://community.st.com/s/question/0D50X0000BOtUflSQF/bug-stm32-lwip-ethernet-driver-rx-deadlock

        do
    {
                sys_mutex_lock(&lock_eth_if_in);
                p = low_level_input( netif );
                sys_mutex_unlock(&lock_eth_if_in);

                if (p!=NULL)
                {
                        if (netif->input( p, netif) != ERR_OK )
                        {
                                pbuf_free(p);
                        }
                }
                else
                {
                        osDelay(10);
                }

    } while(true);