evaluation

Vagelis Hristidis (vagelis@cs.ucsd.edu)
Thu, 4 May 2000 01:42:14 -0700

The Distributed V Kernel and its Performance for Diskless Workstations

V kernel is a message-oriented kernel designed for a local network. Its main
purpose is to serve a network that consists of diskless workstations and
file servers. The paper tries to show that V has comparable performance with
special purpose file access protocols. A main characteristic of the
messaging system of V is that it is synchronous. Processes block when
sending or wait for a message. This simplifies the programming of the
system, but it reduces the flexibility of the system, because we can't
easily simulate the successful event-driven mechanism that is used in
current Operating Systems. There is a distinction between short and long
messages, which improves performance. The kernel implements remote
operations, that makes it more complicated, since the kernel must know the
details of the network. Inter - kernel communication is done with raw
internet protocols to make it faster.

The Sprite Network Operating System

Sprite is a network operating system that is based on UNIX , but also has
some important differences. These differences in the design were motivated
by the new local area network with personal workstations, the larger
physical memories and the multiple processors. RPCs, with some improvements
over UNIX, are used for IPC. The file system has a single hierarchy much
like UNIX, with the difference that this hierarchy changes dynamically,
keeping prefix tables in each machine. Emphasis is given to files caching,
and several mechanisms to preserve consistency are presented. Virtual memory
is implemented using ordinary files, so we have conflicting needs between
virtual memory and files caching for physical memory. Finally Sprite
supports process migration. In general this paper gives some nice ideas that
UNIX creators should think about, in order to stay up to date with the new
computer usage trends and the hardware improvements.