Re: [PATCH 00/12] Add kdbus implementation

From: Alex Elsayed
Date: Thu Oct 30 2014 - 16:28:36 EST


Andy Lutomirski wrote:

<snip>
> There should be a number measured in, say, nanoseconds in here
> somewhere. The actual extent of the speedup is unmeasurable here.
> Also, it's worth reading at least one of Linus' many rants about
> zero-copy. It's not an automatic win.

It's well-understood that it's not an automatic win; significant testing on
multiple architectures indicated that 512K is a surprisingly universal
crossover point. The userspace code, therefore, switches from copying
(normal kdbus parameters) to zero-copy (memfds) right around there.

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