Re: [lwip-users] tcp_enqueue - Does it slow down lwip?

[Kieran Mansley]

On Wed, 2004-12-15 at 19:47 +1030, Paul C wrote:
> Hi 
> 
> I have had a bit more of a dig around the tcp_enqueue() issue. 
> My current work around is in tcp_write, check the return 
> value of tcp_enqueue() if it returns ERR_MEM do a tcp_output and
> retry tcp_enqueue. I think this is beneficial as once
> the queue length is maxed no more can be written so the pcb, so the pcb
> would be stuck until the tcp_tmr tried to send it. It has to be better
> to send it on its way ASAP!

The fact that tcp_write() does not call tcp_output() has been discussed
before, althought I don't remember all the details.  Might be worth
checking the mailing list archive.  I think the outcome was we decided
to document this fact, rather than change the implementation, so there
must have been some negative effect of this action too.  Perhaps
restricting it to only when tcp_enqueue() returns ERR_MEM is a good
compromise though.  

Kieran