linux-kernel - Re: [PATCH 00/12] Add kdbus implementation

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Message-ID: <m2u70q$gtl$2@ger.gmane.org>
Date:	Thu, 30 Oct 2014 13:28:09 -0700
From:	Alex Elsayed <eternaleye@...il.com>
To:	linux-kernel@...r.kernel.org
Cc:	linux-api@...r.kernel.org
Subject: Re: [PATCH 00/12] Add kdbus implementation

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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