Why Resource Manager ?

*When a computer has multiple users, the need for managing and protecting the memory, I/O devices and other devices is even greater.

*The primary task of OS is to keep track of who is using which resource, to grant resource requests, to mediate conflicting requests from different programs etc.

*Users often need to share not only hardware, but information(File, Database) as well.

Which Includes in Resource Manager ?

Resource management includes multiplexing resources in 2 ways, they are

1. In Time

2. In Space

When Resource is Time Multiplexed

*“Who goes next and for how long”- is the main task for time resource manager in OS.

*Different programs or user take turns using it.

*Multiple programs will run by allocating the CPU through OS.

*When another program gets to use the CPU, the OS will choose.

*Sharing the printer is the ideal example for time multiplexing .

When Resource is Space Multiplexed

*Main memory is normally divided up among several running programs

*OS assume enough memory to hold multiple programs

*OS hold several programs in memory at once instead of completing one by one.

*The issues of fairness, protection and so on will solve by OS.

*Hard disk is another resource manager for space multiplexed.

System View - The OS as a Resource Manager

• From the computer's point of view, the OS is the program most intimately involved with the hardware. In this context, we can view an OS as a resource allocator.
• Resource - ``Something valuable'' e.g. CPU time, memory space (RAM), file-storage space, I/O devices (disk), and so on.
• The OS acts as the manager of these resources. Includes multiplexing (sharing) resources in two different ways. Each program gets
  • time with the resource
  • space on the resource
• Multiple users/applications can share, why share:
  • devices are expensive,
  • there is need to share data as well as communicate
• Facing numerous and possibly conflicting requests for resources, the OS must decide
• how to allocate them to specific programs (processes, jobs)
• how to protect applications from one another,
• how to provide fair and efficient access to resources,
• how to operate and control the various I/O devices. 

OR download the slide here : 

Operating Systems: Resource management