Evgeniy Polyakov wrote:
This is what Xen does.  It is actually less performant than copying, IIRC.

The problem with flipping pages around is that physical addresses are cached both in the kvm mmu and in the on-chip tlbs, necessitating expensive page table walks and tlb invalidation IPIs.

Hmm, I'm not familiar with Xen driver, but similar technique was used
with zero-copy network sniffer some time ago, substituting userspace
pages with pages containing skb data was about 25-50% faster than
copying 1500 bytes in general, and in order of 10 times faster in some
cases.

Check a link please in case we are talking about different ideas:
http://marc.info/?l=linux-netdev&m=112262743505711&w=2


I don't really understand what you're testing there. in particular, how can the copying time change so dramatically depending on whether you've just rebooted or not?



--
error compiling committee.c: too many arguments to function

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