Re: [lwip-users] LwIP 1.3.2 -> 1.4.0: Huge RAM increase for PPP use

[address@hidden]

Marco Jakobs wrote:
> Hi Simon,
>
> i'm using Rowley CrossStudio for ARM,

OK, I don't have a MAP parser for that, anyway...

>   but i've found a new buffer which
> consumes most of the increased memory:
>
> /** RX buffer size: this may be configured smaller! */
> #ifndef PPPOS_RX_BUFSIZE
> #define PPPOS_RX_BUFSIZE    (PPP_MRU + PPP_HDRLEN)
> #endif
>
>
> This is around 1.5k and was not there in 1.3.2 ... however, there is no
> advice in the code how "small" it can be defined to be still useful (and
> what this buffer does).

I thought of something in that direction... In 1.3.2, this buffer has 
been allocated from a PBUF_RAM pbuf. This was kind of broken from the 
design point: PBUF_RAM is mostly used for TX while PPP used it for RX - 
this could mean that allocating too much TX buffers could block RX.

Anyhow, the total amount of memory used by lwIP hasn't been changed by 
this: the only change is that now, the memory is allocated statically, 
while before that allocation was hidden inside 'ram_heap' (defined in 
mem.c).

I'm still open for a good proposal for a change, if you have one...

Simon