Message-ID: <CABDyM6Qzm3nfQDD1mHcQ58JUVECaPdukTB+b5-WxP=iqoONF4w@mail.gmail.com>
Date:	Sun, 26 Feb 2012 16:25:51 -0500
From:	Richard Yao <ryao@...stonybrook.edu>
To:	Ted Ts'o <tytso@....edu>, Richard Yao <ryao@...stonybrook.edu>,
	Bernd Petrovitsch <bernd@...rovitsch.priv.at>,
	Henrik Rydberg <rydberg@...omail.se>,
	Bobby Powers <bobbypowers@...il.com>,
	Greg KH <gregkh@...uxfoundation.org>,
	Guenter Roeck <guenter.roeck@...csson.com>,
	Jidong Xiao <jidong.xiao@...il.com>,
	Kernel development list <linux-kernel@...r.kernel.org>
Subject: Re: Can we move device drivers into user-space?

Ted,

I think you have me confused with Jidong Xiao. He is the one who
suggested moving things to userspace. I happened to see the
conversation, noticed people had missed a few points and added them in
an attempt to be helpful. If you look at my emails to the mailing
list, you would see that I had said that this work should be done
elsewhere. The email to which you had replied was one that was meant
to say that if people were set on having those interested in doing
this to work with LInux, it should be okay for them to brainstorm on
the LKML.

With that said, please refrain from further outbursts. They hurt Linux.

Yours truly,
Richard Yao

On Sun, Feb 26, 2012 at 3:30 PM, Ted Ts'o <tytso@....edu> wrote:
> On Sun, Feb 26, 2012 at 10:05:59AM -0500, Richard Yao wrote:
>> >> I do not see what prevents an in-kernel context switch into a ring 3
>> >> context with a different process address space. Is it necessary to
>> >> remove the code from the kernel tree before someone can do this?
>> >
>> > No, and that's the real problem here: Everybody who might think it's a
>> > good idea may please implement - and thus propose - something concrete,
>> > try it out and comeback with experience and performance numbers - and
>> > not just try to come up with some theory and other misleading points
>> > (what political aspect?!) and ideas what others should do and why it
>> > might be better.
>>
>> It seems counterproductive to tell people to produce results without
>> doing the brainstorming that such results require.
>
> It's also counterproductive to tell kernel programmers how they should
> do what they are being paid how to do.  If you just want to brainstorm
> possibilities where **you** will do all of the work, as opposed to
> asking the kernel development community to work on your pet theories,
> it's helpful if you more carefully label your poposals as such.
>
>> If such discussion is not welcome here, then the FreeBSD project has a
>> similar kernel design. Perhaps it would be more productive for those
>> interested in this to brainstorm on their mailing list. If anything
>> materializes, it could be for their kernel instead. Nothing is forcing
>> anyone to do things with Linux.
>
> My experience is that most researchers produce code which is not of
> production quality.  It's very easy to produce a proof of concept that
> works well enough to publish a paper.  Making something which is
> actually performant, is **hard**.  The problem is that you don't get
> Ph.D.'s for counting cache line misses --- or for getting your
> implementation to the point where cache line misses matter in the
> first place.  So the threat that Linux will miss out on some great
> breakthrough is something that is very hard for me to take seriously,
> speaking quite frankly.
>
> Usenix has awarded best paper awards to work that was done on obsolete
> kernels, where if the goal of that work was to produce production
> kernel code, was in fact horrible work.  But if the goal of that work
> is to produce Ph.D. graduates, or to help the professor get tenure,
> was perhaps more successful.
>
> That being said, maybe you'd be happier engaging with the Minix 3
> community.  They are folks who think (unproven, theoretical) safety is
> more important than performance.  And they've created a kernel which
> is a 140 times slower at process creation, ten times greater syscall
> overhead, and file copies that were two to ten times slower.[1]
>
> [1] http://lwn.net/Articles/220255/
>
> And Prof. Tannenbaum is an academic, so his goals may be more closely
> aligned to yours.
>
> Best regards,
>
>                                           - Ted
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