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Memory Organisation
Published in Pranabananda Chakraborty, Computer Organisation and Architecture, 2020
It has been observed that most programs do not reference their logical address space uniformly, rather randomly access only a small number of pages forming a set, and the changes in this set then occur slowly with time. The pages whose addresses are referenced during the time interval from (t − t1) to t denoted by (t − t1, t) constitute the working set w (t, t1). An alternative definition proposed by Denning is that at any instant time, t, there exists a set consisting of all pages used by the k most recent memory references. This is defined as working set w(k, t). This k is sometimes called the window size of the working set. Only the working sets of active processes are resident in main memory. It has been found that k + 1 most recent references must have used all the pages used by the k most recent references, and possibly others. If the working set is not properly maintained, then page faults are generated frequently and continuously, resulting in what is called thrashing. This makes a constant to and fro journey of pages from virtual memory causing unnecessary additional overhead (to service frequent page-fault interrupts) resulting in severe performance degradation.
Evaluation criteria for holonic control implementations in manufacturing systems
Published in International Journal of Computer Integrated Manufacturing, 2019
To assess the computational resource requirements, two measures are used: CPU time – as an indicator of CPU usage, CPU time is the measurement of the combined time, over all available cores, that the CPU executes instructions for the holonic control implementation (Microsoft TechNet, 2018a). CPU time can be measured by the operating system and in Windows is available in the processes window of the Task Manager application. The CPU time should be recorded at the start of production (thus the CPU time involved with system start-up is excluded) and again when production of the last product is completed.Memory usage – the random access memory (RAM) consumed by each implementation is monitored during simulated production. Windows includes the Performance Monitor application, which allows the user to record many of the counters exposed by the operating system. There exist counters for every active process on the PC. The Private Working Set counter measures the RAM (in bytes) that is consumed by a single process (Microsoft TechNet, 2018b) – this counter should be recorded for the duration of a production run.