Re: [lwip-users] Custom placement of memory pool

[Giuseppe Modugno]

Il 09/11/2018 04:05, uaz ha scritto:
> Hi all,
>
> I'm currently running lwip v2.0.3 on LPC4357 platform.
> I have some issue with pbuf mem_alloc(), which I believe is fragmentation
> issue because after several packet transfers, I'm unable to allocate pbuf
> anymore.

I don't know if it is the same problem I faced some months ago with the 
MCU LPC1769.

I found a behaviour similar to the one you are describing. After some 
HTTP requests (received and answered correctly), no more HTTP requests 
are possible. Consider that the problem appeared only with HTTP requests 
that needed custom file (as internal lwip http server nomenclature).

The solution I found is defining MEMP_MEM_MALLOC to *0/zero* (it was set 
to 1/one). When set, this macro enables mem_malloc/mem_free for pools 
management (so dynamic management instead of static management). In my 
case, mem_malloc/mem_free are effectively malloc/free of newlib C 
standard library (because I defined MEM_LIBC_MALLOC to 1).

Here[1] you read the definition of MEMP_MEM_MALLOC macro:

> MEMP_MEM_MALLOC==1: Use mem_malloc/mem_free instead of the lwip pool 
> allocator. Especially useful with MEM_LIBC_MALLOC but handle with care 
> regarding execution speed (heap alloc can be much slower than pool 
> alloc) and usage from interrupts (especially if your netif driver 
> allocates PBUF_POOL pbufs for received frames from interrupt)! 
> ATTENTION: Currently, this uses the heap for ALL pools (also for 
> private pools, not only for internal pools defined inmemp_std.h 
> <http://www.nongnu.org/lwip/2_0_x/memp__std_8h.html>)!
I think the NXP Ethernet driver implementation isn't compatible with 
MEMP_MEM_MALLOC. Anyway I'm not sure, because the problem happens only 
for "custom file" http requests and not for every request.

[1] 
http://www.nongnu.org/lwip/2_0_x/group__lwip__opts__mem.html#gae93af697d27bbcefa6a28052d90f2f38

> Right now I'm switching to custom memory pool approach, but I'm consuming
> more SRAM than available, thus the project is not compiling.
>
> Is there any way to manually place memory pool to a certain address?
>
> Thanks,
> UAZ
>
>
>
> --
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>
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