9.28: Consider a demand-paging system with the following time-measured utilizati
ID: 3764020 • Letter: 9
Question
9.28: Consider a demand-paging system with the following time-measured utilizations: CPU utilization 20% Paging disk 97.7% Other I/O devices 5 %
For each of the following, say whether it will (or is likely to) improve CPU utilization. Explain your answers. a.) Install a faster CPU. b.) Install a bigger paging disk. c.) Increase the degree of multiprogramming. d.) Decrease the degree of multiprogramming. e.) Install more memory. f.) Install a faster hard disk or multiple controllers with multiple hard disks.
Explanation / Answer
Under Demand paging system - memory is increased only as per demand of the program.
best choice is c) Increase the degree of multiprogramming
Below are the explanations for each.
a) Install a Faster CPU : Installing a faster CPU will only decrease the time of processing hence, CPU would be more free than ever - CPU Utilization will sill readuce here not much is saved in memory consumption.
b) Install a bigger paging disk: This will help in loading a bigger program or allocate more memory to the current program. If this is expanded, cpu would be a little free from managing tight memory addressing issue.
c) Increase the degree of multiprogramming - This is the best option in this case - in demand - paging system all the memory is allocated to the program at once, if the current programs are taking 97.7% of memory and CPU is at 20%, that means programs are taking memory and are still not being closed - to be closed CPU must be free, in this case CPU is also free - so programs are not multithreaded - if multui threaded - the programs would be closed freeing menory by then or CPU will be utilised to full extent
d) Decrease the degree of multiprogramming - Two ways of understanding this
1) If the program is really memory intensive rather than computing - them multithreading should be reduced since a bottleneck at memory allocation on priority would come into picture.
2) If the program is not memory intensive - then more momory is getting stuck - no proper garbage collection is working here - threads are created and not killed blocking memory.
e) Install More Memory - This is always a good option since current memory consumption is high - but this is basicall based on how the program is executing or type of program etc example video converions take a lot while as computing scitific data takes less then 5% of that.
f) Install a faster hard disk or multiple controller with multiple hard disk - Installing faster HDD like SDD or installing multiple hard disks in raid only benefit at initialization of program for loading the files. Example in game - more files are to loaded before starting, or in FTP servers where only disk based operations are to be performed. This helps only on file based activities.
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