Paper Evaluations

Kiran Tati (ktati@csag.ucsd.edu)
Tue, 18 Apr 2000 00:45:14 -0700

Pilot
The goal of the pilot operating system is to provide major facilities
that are available on large multi user system. I think at that time the
operating system for the PC doesn't have these facilities, So this is
new in this paper. Another interesting idea is just provide the some
functionality which is required to implement a single language run time
system. So all of the operating system functionality is visible through
the Mesa language in interface form. This operating system provide a
flat
file system which is consistent with file system design at that time.
Another novel feature of this operating system is integration of virtual

memory with the file system. Streams are not a new feature but it
provide
another way of accessing devices. It's not clear from the paper about
virtual address space of each process but in the Opel paper they
mentioned
that pilot used single address space. It also implemented a network
protocol
similar to the TCP/IP. The major disadvantage is that the system is
tightly
coupled with single language. This forces everybody to use one language.

But implementing other runtime systems for object oriented languages is
not a big problem and I think they can exists simultaneously.

Opel:
The main goal of this project is reduce the cost of inter process
communication cost while maintaining protection guarantees. The approach

taken in this project is provide one big virtual memory so that
address space is shared by all process that ever run on
this operating system. So in this scenario the inter process
communication
is equivalent to the accessing the memory. Another aspect of this system

is that one can share pointer based data stractures very easily. One
real
advantage with system is that it disambiguate the virtual tags in
processor
caches. The address reuse is necessary so some address reuse mechanisms
should provide. Unfortunately this aspect is not well discussed in the
paper.
Another disadvantage is that this approach uses an order of magnitude to

represent a same amount of address space in terms of number of bits
required
to represent the process address space.

--
Kiran Tati (Graduate Student)            Kiran Tati
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