Date: Wed, 15 Apr 2015 13:20:37 -0400
From: Steven Rostedt <rostedt@goodmis.org>
To: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Cc: Borislav Petkov <bp@alien8.de>, Richard Weinberger <richard@nod.at>,
        Andy Lutomirski <luto@amacapital.net>,
        Al Viro <viro@zeniv.linux.org.uk>,
        "Eric W. Biederman" <ebiederm@xmission.com>,
        Linus Torvalds <torvalds@linux-foundation.org>,
        Andrew Morton <akpm@linux-foundation.org>,
        Arnd Bergmann <arnd@arndb.de>,
        One Thousand Gnomes <gnomes@lxorguk.ukuu.org.uk>,
        Tom Gundersen <teg@jklm.no>, Jiri Kosina <jkosina@suse.cz>,
        "linux-kernel@vger.kernel.org" <linux-kernel@vger.kernel.org>,
        Daniel Mack <daniel@zonque.org>,
        David Herrmann <dh.herrmann@gmail.com>,
        Djalal Harouni <tixxdz@opendz.org>
Subject: Re: [GIT PULL] kdbus for 4.1-rc1
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On Wed, 15 Apr 2015 18:40:33 +0200
Greg Kroah-Hartman <gregkh@linuxfoundation.org> wrote:

> On Wed, Apr 15, 2015 at 11:41:53AM -0400, Steven Rostedt wrote:
> > 
> > And obviously there is a lack of trust. And once kdbus is in, we must use
> > it, or support our own distro where we just do not have the time.
> 
> Just like cgroups, and ftrace :)

Exactly.

> 
> > Personally, I'm fine with getting something in that will help userspace
> > tools work better. The issue I see, mostly from the side lines as I haven't
> > totally submerged myself into the dbus protocol (I think I should spend
> > some time to do just that), this is going too fast. Once it is in the kernel,
> > whatever ABI we expose is locked in stone. There's no changing it. We need
> > to make sure that this is well thought out. People seem to be of the impression
> > that the current dbus design has flaws, but because everything relies on it
> > we must still push it into the kernel because it mimics what is out there
> > in user space. I disagree.
> 
> "fast"?  Are you kidding me?  This stuff has been under active, public,
> development for over two years.  We have been posting public patches,
> asking for review and comments for _months_ now.  Given that there were
> no more specific review comments on the patch set, and its success in
> linux-next for almost the entire 4.0 development cycle, I asked it to be
> merged.
> 
> I don't know too many other kernel features/drivers that have taken this
> long, or done this "slowly", do you?

What other features/drivers that you know introduce a major new IPC
user space interface that will be a core component of the system?

> 
> > As others have said. We do not need to follow the dbus design. If we can supply
> > a better transport layer than what the kernel supplies today, then tools will
> > eventually merge to it away from dbus. Perhaps the kernel can supply just enough
> > to have dbus improve its speed, but not with the entire complex solution that
> > kdbus is presenting today.
> 
> I originally thought this would work too.  8 months of work later, I was
> proven wrong, that will not work.  Or it imposes too much additional
> work on userspace that really makes no sense at all.  The in-kernel code
> isn't a lot (again, 13k lines, smaller than almost all of the drivers
> you are using today on an individual basis)  It's also really fast, but
> with benchmarks, David and Andy have found some minor bottlenecks that
> can make things faster.
> 
> Yes it seems complex, but read the documentation to get an idea of what
> is happening here.  I think you will get a better appreciation of what
> is going on.

I read a bit of the documentation, but not enough. I really need to sit
down and play with code. That's the way I learn and understand.

-- Steve
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