Simon Goldschmidt wrote: > Still, I think lwIP should be able to achieve the performance you want if: > A) your netif driver correctly supports zero copy
A few months ago(*) we discussed zero-copy for DMA drivers, and you wrote: > For the RX side, using a *custom* PBUF_REF would be the best solution. > That's a pbuf that has a 'freed' callback and references external > memory. However, that doesn't work, yet (though I planned to add support > for it as I can see it's one possible solution to implement DMA MAC > drivers). The problem here is that pbuf_header() can't grow such pbufs > (as it doesn't know the original length). This would have to be fixed by > changing the struct pbuf (if only for PBUF_REF pbufs). Is this mode supported in the trunk? If yes, do you plan to port it to 1.4.1? If no, that means I have to memcpy every incoming frame, right? > As to the TX side: normally, TX pbufs are allocated as PBUF_RAM, the > memory for that is taken from the heap by calling mem_malloc(). Now the > simple solution would be to just replace mem.c by your own code > allocating and freeing from your TX pool: with the correct settings, > mem_malloc() isn't used for anything else buf PBUF_RAM pbufs. The only > problem might be that you don't know in advance how big the memory > blocks are (and thus how big your TX buffer entries should be), but by > using TCP_OVERSIZE, you can just use the maximum ethernet frame size (if > you don't mind wasting some RAM for smaller packets). But when I looked, I don't think it's possible to use mem_malloc as a packet buffer allocator, as there are other types of uses, e.g. dhcp = (struct dhcp *)mem_malloc(sizeof(struct dhcp)); autoip = (struct autoip *)mem_malloc(sizeof(struct autoip)); What I'd like is to be able to "redirect" pbuf_alloc to use my buffer allocator, but the pbuf struct and the payload buffer would not be contiguous, which violates the implicit assumptions of PBUF_RAM pbufs, IIUC. Have things changed on that front? If no, that means I have to memcpy every outgoing frame, right? (*) Date: Thu, 06 Oct 2011 16:10:07 +0200 http://lists.gnu.org/archive/html/lwip-users/2011-10/msg00008.html -- Regards. _______________________________________________ lwip-users mailing list [email protected] https://lists.nongnu.org/mailman/listinfo/lwip-users
