Re: zero-copy TCP

Date: Sun Sep 03 2000 - 09:20:22 EST

Ingo Molnar wrote:
> On 2 Sep 2000, Jes Sorensen wrote:
> > Besides that you need to do copy-on-write if you want to be able to do
> > zero copy on write() from user space [...]
> i agree that this is hard - i'm not sure wether we want to go the pain to
> enable anonymous-buffer write()s do zero-copy.

If we go for a Linux-specific solution anyway, maybe one could add
another send{,to,msg} flag that makes send*(2)'s buffer access
non-atomic. That way, the kernel only needs to make sure the pages
don't disappear, but there's no need for expensive MMU games.

Of course, this would give applications a way for generating packets
with an incorrect TCP/UDP checksum, so maybe that should be protected
by a capability then, maybe CAP_NET_RAW.

- Werner

 / Werner Almesberger, ICA, EPFL, CH /
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