Mason wrote: > 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
I did find this information on the lwip wiki http://lwip.wikia.com/wiki/Writing_a_device_driver#Notes_on_Zero-Copy_Network_interface_drivers But I think it's a little bit dated? -- Regards. _______________________________________________ lwip-users mailing list [email protected] https://lists.nongnu.org/mailman/listinfo/lwip-users
