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Re: "Microkernels rule!" and the Hurd

From: Arne Babenhauserheide
Subject: Re: "Microkernels rule!" and the Hurd
Date: Mon, 25 Aug 2008 07:53:05 +0200
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Hi Neal, 

Many thanks for your information! 

Could you write a counter-story/public reply for the Hurd-Wiki? 

It needn't be long, but it should be available online. 

Best wishes, 

Am Mittwoch 13 August 2008 10:04:29 schrieb Neal H. Walfield:
> Gernot Heiser recently wrote an article, "Microkernels rule!" for
> Embedded.com about microkernels' bad reputation.  I fully agree with
> the message of his article: operating systems based on microkernel
> technology don't necessarily have to be slow and can be made more
> robust than their monolithic counterparts.  However, Gernot mentions
> the Hurd and incorrectly describes its position in history:
>   Mach, an OS that was widely used as the basis of systems, ran into
>   serious performance problems...  There were spectacular failures,
>   none more so than IBM's Workplace OS, which cost the company a cool
>   two gigabucks...
>   Needless to say, the experience with Mach and others created a bit
>   of an image problem for microkernels (which didn't stop the GNU Hurd
>   from repeating the mistakes of the past).  However, back in 1993,
>   Jochen Liedtke demonstrated that these performance problems weren't
>   inherent in the microkernel concept.
> The Hurd did not repeat the errors of past.  Work on the Hurd started
> in 1990.  In GNU's Bulletin January, 1994 [1], you'll find an article
> detailing the Hurd's architecture.  Workplace OS was conceived in
> 1991; it was deemed a failure around 1995.  Jochen's article
> "Improving IPC by Kernel Design" was published in December 1993.
> Regarding, Workplace OS, its main goals were: machine independence,
> multiple personalities, and concurrent operation of personalities [3].
> The last two goals, as far as I am aware, were never a priority in the
> development of the Hurd.  Further, Workplace OS had already adopted
> many second generation microkernel features, for instance, L3's
> synchronous IPC.  In the major "Observations and Lessons" section of
> [3], this is not even mentioned; management, coordination, and focus
> are cited as the major problems.
> Finally, the architectural problems that we have identified with Mach
> [4] are not related to IPC.  The most important are the lack of
> resource accounting, and the bad resource management (paging
> decisions).  Regarding the implementation that we use, the major
> problems are unoptimized code (e.g., when evicting a bunch of pages,
> Mach always sends them one at a time to the manager), and the decades
> old code base which was designed for machines with tens of megabytes
> of RAM.
> Neal
> [0] http://www.embedded.com/columns/guest/208800243
> [1] http://www.gnu.org/bulletins/bull16.html#SEC13
> [2] Improving IPC by kernel design
>     Jochen Liedtke
>     SOSP December 1993
>     http://portal.acm.org/citation.cfm?id=173668.168633
> [3] Workplace Microkernel and OS: A Case Study
>     Brett D. Fleisch and Mark Allan A. Co
>     Software--Practice and Experience
>     May 1998
>     http://portal.acm.org/citation.cfm?id=279869.279875
> [4] A Critique of the GNU Hurd Multi-server Operating System
>     Neal H. Walfield and Marcus Brinkmann
>     ACM SIGOPS Operating Systems Review
>     July 2007
>     http://portal.acm.org/citation.cfm?id=1278901.1278907

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