Re: [PATCH v4 00/14] Add kdbus implementation

On Mon, Mar 9, 2015 at 6:09 AM, Greg Kroah-Hartman
[off-list ref] wrote:

kdbus is a kernel-level IPC implementation that aims for resemblance to
the the protocol layer with the existing userspace D-Bus daemon while
enabling some features that couldn't be implemented before in userspace.

[...]

What changed from last time?

The discussion from last time about performance seems to have stalled.
kdbus is supposed to be fast -- that seems to be a large part of the
point.  Can anyone comment on how fast it actually is.  I'm curious
about:

 - The time it takes to do the ioctl to send a message

 - The time it takes to receive a message (poll + whatever ioctls)

 - The time it takes to transfer a memfd (I don't care about how long
it takes to create or map a memfd -- that's exactly the same between
kdbus and any other memfds user, I imagine)

 - The time it takes to connect

I'm also interested in whether the current design is actually amenable
to good performance.  I'm told that it is, but ISTM there's a lot of
heavyweight stuff going on with each send operation that will be hard
to remove.

--Andy