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

From: address@hidden
Subject: Re: [lwip-devel] Fwd: Re: TCP errors going from 1.4.1 to 2.0.3
Date: Wed, 1 Nov 2017 20:14:49 +0100
User-agent: Mozilla/5.0 (Windows NT 6.1; WOW64; rv:45.0) Gecko/20100101 Thunderbird/45.8.0

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?


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