We call it PRE-requirements. When a system can trade P for R or E and vice versa
we call this system PRE-smart system. This chapter is about “P”—performance.
Any system is evaluated in terms of performance, considering performance of
elements and system as a whole. Good systems exceed performance of their
components, or equal production of component performance; badly design system
in terms of overall performance is much less than production or sum of performances of its components. Regretfully, computer systems are poorly designed if we
accept this classification. This chapter is about performance and ways to analyze it.
We also will model computer system from the position of performance and seeking
the ways to improve it, considering use and system performance aspect.
17.1 System Level
Suppose one element has performance Pi; then system of n elements if we can add
performance will have maximum performance as n*Pi, i.e., linear growth is assumed.
Unfortunately, one has to take into account that external interaction zone (Fig. 17.1)
and task structure reduce our expectations about unlimited performance growth.
ACTIVE
ZONE (AZ)
EXTERNAL
INTERACTION
ZONE (EIZ)
ACTIVE
ZONE (AZ)
ACTIVE
ZONE (AZ)
ACTIVE
ZONE (AZ)
ACTIVE
ZONE (AZ)
ACTIVE
ZONE (AZ)
ACTIVE
ZONE (AZ)
ACTIVE
ZONE (AZ)
ACTIVE
ZONE (AZ)
ACTIVE
ZONE (AZ)
ACTIVE
ZONE (AZ)
Fig. 17.1 System level of distributed computing
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17 On Performance: From Hardware up to Distributed Systems