Re: [lwip-devel] Fwd: Re: TCP errors going from 1.4.1 to 2.0.3

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Bill Auerbach wrote:
> I was using pointers to pbufs and pbuf->payloads with the "don't 
> cache" bit set so I could DMA into and out of this memory without 
> overhead.

Ehrm, maybe I can understand why you return pbuf->payload as uncached, 
but handling pbufs uncached as well seems totally unperformant. Have you 
actually *benchmarked* accessing everything uncached vs. cache flushing 
before TX/after RX?

If you insist, one idea could be to just "move" the pools in question to 
uncached memory instead of changing pbuf.c. That might not work for 
PBUF_RAM though...

> Pbuf allocation between 1.4.1 and 2.0.3 must be different

I can't tell what's changed.

> I know Simon, you use (used) the NIOS II and maybe you could comment 
> on this or tell me if you think this optimization is worthwhile. 

I don't have current numbers (we're not really using that platform any 
more), but I went for cache flushing in the last product with the NIOS 
II and didn't have any problems.
How would your patch look like?

Simon