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ficient is because the Exokernel is leaner - largely
because protection mechanisms that usually get
duplicated in a traditional operating system are
not present.
Therefore, local optimizations do in fact support
the global optimization of the Exokernel.
exokernel's file Storage
Scheme enhances run-time
aggressive applications are
Significantly times faster
The researchers conducted experiments to test
what Robert Grimm calls the Exokernel's “fine
grained interleaving of disk storage” (Grimm,
1996). In the experiments, two applications were
compared as they each accessed 1,000 10-KByte
files. The Ekokernel's “fine grained interleaving”
seems to account for a 45% faster file access time
than that of an operating system that does not use
this “fine grained interleaving” approach. The
Exokernel's flexibility also seems to be respon-
sible for allowing the Exokernel to conduct “file
insert” operations about 6 times faster. These test
results seem to support the conclusion that the
Exokernel's file storage scheme does enhance the
over-all run-time of the operating system.
One of the goals of the extensible approach of the
Exokernel is that its performance can be optimized.
In order to test this theory, researchers attempted
to make optimizations to applications running on
an Exokernel system. As an experiment, XCP and
CP were tested against each other. Although XCP
and CP are both file copy programs, XCP is a file
copy program that is optimized to take advantage
of the flexibility of the Exokernel Operating Sys-
tem. The test results show that the XCP file copy
program can complete its tasks about three times
faster than that of CP. Other experiments were
also conducted to test the speed of a Cheetah web
server. The Cheetah web server, when running
on top of the Exokernel OS (Xok), was found to
be four times faster, for small documents. These
results support the claim that the Exokernel OS
does allow the user to optimize application code
to achieve significant speed-ups in processing
speeds.
actiVe networKing
One of the technologies that has benefited from
the Exokernel is Active Networking. The concept
of an active network evolved from research being
conducted at the DefenseAdvanced Research Proj-
ects Agency. This group is known for developing
the “DARPA Internet”, which is the foundation
for our modern day Internet.
In a traditional network like the Internet, data is
passively transported from a start point to an end
point. Along its journey, the data passes through
nodes that route the data packets based on header
information while ignoring the actual data found
in the packet contents. In the words of David L.
Tennenhouse and others, the DARPA research
community identified the following problems
with networks;
local control can lead to
enhanced global performance
The Exokernel researchers wondered if only
specific processes can be optimized, or if the
global performance of an operating system can be
optimized. The researchers tested the Exokernel
as it ran multiple applications concurrently and
compared the results with non-extensible operat-
ing systems. The results show the Exokernel is, at
least, as efficient as the non-extensible operating
systems. Furthermore, after an Exokernel Operat-
ing System is optimized - what the researchers
have called “local optimizations” - the “global
performance” of the Exokernel is also enhance.
1.
“The difficulty of integrating new technolo-
gies and standards into the shared network
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