Ask the Expert

Methods to improve CPU utilization

Consider a demand-paging system will follow the time - measured utilization:

CPU utilization 20%
Paging disk 97.7%
Other I/O devices 5%

For each of the following, can you tell me whether it will improve CPU utilization?

Install a fast CPU
Install a bigger paging disk
Increase the degree of multiprogramming
Decrease the degree of multiprogramming
Install more main memory
Install a faster hard disk, or multiple controllers with multiple hard disk
Add prepaging to the page fetch algorithms
Increase the page size


  • Install a fast CPU: No

  • Install a bigger paging disk: No
    (But I'm not sure what's meant by 97.7% paging disk utilization. If the system runs out of pagefile space, it'll stop allocating memory, which would cause apps to shut down.)

  • Increase the degree of multiprogramming: Does this mean multithreading? If so, increasing the multithreading of an application could help if most of the utilization comes from that single application.

  • Decrease the degree of multiprogramming: No

  • Install more main memory: Yes, this is your best bet.

  • Install a faster hard disk, or multiple controllers with multiple hard disk: Yes, but installing more memory is a better idea.

  • Add prepaging to the page fetch algorithms: Perhaps marginally.

  • Increase the page size: No

    This was first published in March 2002

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