[TUHS] OT: critical Intel design flaw

Theodore Ts'o tytso at mit.edu
Thu Jan 4 09:40:25 AEST 2018

On Wed, Jan 03, 2018 at 01:27:19PM -0500, Clem Cole wrote:
> > This slowdown (which is not much -- L4 shows it is about 5% or so)
> >
> ‚ÄčI agree.   We came to the same conclusion in the early/mid 1990's  with
> Mach and Chorus.   In fact, the UI 'requirements for modern OS' document
> (which is part of why AT&T got behind Chorus for the never completed
> SVR5/R6 stuff - I'll see if I can find a copy) was based on that work.
> The OS weenies at the time felt that the cost was low enough and hardware
> cheap enough that of course kernels would be the way to go.

It's possible to keep the slowdown at 5%, but how much extra
engineering work does it take to get the performance gap down to that
level?  And during that time while the micro kernel team is playing
catchup, if the OS with the monolithic kernel adds new features to the
OS, how much additional time does it take to add those features to the
OS?  (Regardless of whether the features are implemented in userspace,
or in the kernel, or some combination of the two.)

> Similarly, Microsoft since Windows (not OS/2) was the UI for NT in the end;
> Microsoft had to put hacks into the make user code word and NT became a
> hybrid (like Mach 2.x) and never pushed the pure kernel that Mica (NT's
> origin had been). To do so would have broken code which at the time was
> something they were loath to do.

Actually, at least part of the problem was that graphics performance
was *terrible*.  So in NT 4.0 they moved it into the kernel for
performance reasons.  One could argue that with enough effort, the
graphics performance perhaps could have been improved while keeping
within the microkernel design principles.  But in the commercial
marketplace, timing is everything; and even being six months late to
the game can be enough to lose the battle for mindshare.

(There are those who have argued that the *BSD's were delayed by
around six months due to the AT&T / Berkeley lawsuit, and if it were
but for that, Linux would not have gained the prominence that it
had/has.  I'm not completely sure I buy that; there were *BSD
developers in the Boston area, and it was primarily because of a
certain toxic personality that they failed to lure me to the *BSD side
of the force --- and I got my start working kernels with BSD 4.3+ at
MIT Project Athena.  Despite how people like to complain about Linus's
shortcomings in that department, let's just say that IMHO there are
*far* worse personalities in the open source OS world, and leave it at

> The hope is a new disruptive market -- as you say.  Maybe Arm/Cell phones
> will be that.  I would not bet against them, but then again.   IBM/Intel *et
> al *have a history of recovering.    It is going to be interesting to both
> watch and play the game for the next few years -- UNIX is hardly dead nor
> traditional complex systems that run on them, nor the HW that delivers it
> :-)

Well, Fuchsia is based on a microkernel, and one interesting thing
about it is that full POSIX compatibility is *not* a goal.  The team
is apparently not worried about legacy support (where they consider
Linux and Unix "legacy") and performance on HDD's is also a legacy
issue.  (It's the 21st century, except for big data centers at Google,
Facebook, Microsoft, et. al, who uses disk drives in this day and

There will be rough POSIX compatibility, but it is refreshing that
they don't consider horrendous design decisions (e.g., such as telldir
and seekdir) things that they are bound to support.

Of course this means no X11, no GNOME, no KDE, etc.  (And because
there is no telldir/seekdir, no Samba support, either.  Oh, well.  Who
needs to serve CIFS, anyway?)  All graphical applications that want to
run on Fuchsia have to be rewritten to use graphics SDK called
"Flutter".  It'll be interesting to see what happens with this
approach, and whether it can supplant the Linux/Unix ecosystem.

       		   	    		   - Ted

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