4 research outputs found
Studies of some feedback control mechanisms in operating systems
PhD ThesisThe possibility of enhancing the effectiveness of an
operating system by the introduction of appropriate
feedback controls is explored by examining some
resource allocation problems. The allocation of
and I/O processors in a multiprogramming core, CPU
demand paging environment is studied in terms of
feedback control.
A major part of this study is devoted to the application
of feedback control concepts to core allocation to
prevent thrashing and develop algorithms of practical
value. To aid this study a simulator is developed
which uses probability distributions to represent
program behaviour. Successful algorithms are developed
employing a two stage page replacement function which
selects a process from which a page is then chosen to
be replaced. Improving the performance of these
algorithms by using a 'drain process' to aid the
dynamic determination of the current locality of a
process is also discussed.
The complexity of the overall resource allocation
problem is dealt with by employing a hierarchy of
individual resource allocation policies. These
control scheduling, core allocation and dispatching. By considering the levels of the hierarchy as separate
feedback control systems the restrictions which must
be placed upon the individual levels are derived. The
extension of these results to further levels is also
discussed.Science Research Counci