From: Steve Arnold (stevearn_at_microsoft.com)
Date: Wed Jan 14 2004 - 17:07:13 PST
The authors of this paper explain their Exokernel system and why it
performs better than a typical OS. The Exokernel system given regular
applications more control over controlling resources without having to
trust them as part of the kernel. They explain that this brings up many
issues.
Much concentration is given to XN, the flexible stable storage system.
It allows great flexibility to have multiple file systems on the system
at one time. It also provides a discussion of how you then provide
mechanisms to share amongst those systems. I won't go into the details
here, but there are many coherence and other requirements that must be
followed to make it work, while still allowing as much control as
possible.
Next they go on to explain Xok. This is more of the kernel part, where
memory and processes are managed. On top of Xok, they built ExOS, which
is an application that provides many OS-type utilities. As part of their
research they implemented many UNIX abstractions through this.
In the final section of the paper, they conclude with a performance
discussion. Even the base system performance on traditional tasks, they
contend, perform better. However the real gain comes from custom
designing your applications to manage system resources. Their primary
example is in a web server.
The authors present some convincing arguments. I would have liked to
have a higher level overview of their system, as I didn't follow some of
the implementation details. It seems though that you still give up some
advances in stability in order to achieve more performance.
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