zero_copy in RTEMS

Chris Johns chrisj at
Sun Dec 21 20:02:34 UTC 2008

Gene Smith wrote:
> ??? wrote, On 12/19/2008 07:14 AM:
>> Hi all:
>>        Does anyone know how to implement zero copy in RTEMS ?
>>        Thanks in advance.
> I assume you are referring to the tcp/ip stack? I think some DMA 
> controllers can put their inputs and accept outputs directly from BSD 
> mbufs (like EMAC on ppc405gpr controller). 

Same with the Coldfire FEC.

> But I am not sure how many 
> other places (or even if) the packets are memcpy'd in the stack.

Only when placing the data into your buffer when receiving or taking it out to 
send. The mbufs are part of the implementation and not part of the socket API 
so a copy is needed at that interface.


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