Re: is CONFIG_PACKET_MMAP always a win?

Alan Cox (alan@lxorguk.ukuu.org.uk)
Sat, 23 Feb 2002 00:24:35 +0000 (GMT)

> > 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?

It accesses system memory. That means the copy you have in cache is stale
so you need to get rid of the copy in the cache - be that software or
hardware.

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