On Fri, Feb 22, 2002 at 07:57:33PM +0000, Alan Cox wrote:
> > > You can process them in the ring buffer. If you can't keep up then you
> > > are screwed any way you look at it 8)
> >
> > That still doesn't avoid copying: af_packet copies the whole packet (if
> > you want the whole packet) from the original skbuff to the ring buffer.
>
> I'd make a handwaved claim that the first copy of the packet from a DMA
> receiving source is free. Its certainly pretty close to free because the
> overhead of sucking it into L1 cache will dominate and you need to do that
> anyway.
>
Doesn't DMA access system memory directly and leave processor caches alone?
If so, then the fewer copies that have to pollute the L1/2 caches the better.
Even if it does for UP, I'd immagine that it doesn't for SMP...
Mike
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This archive was generated by hypermail 2b29 : Sat Feb 23 2002 - 21:00:46 EST