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Difference between Virtual Memory and Job Pool

Both virtual memory and job pools temporarily store the processes on disk and bring them to memory later. When a process is just created, it first goes to the job pool and then is sent to the ready queue. Virtual memory is only used when available memory becomes smaller than the required memory for any process.

In this article, you will learn about the difference between virtual memory and job pool. Still, before discussing the differences, you have to know about the virtual memory and job pool in the operating system.

What is Virtual Memory?

A computer can address more memory than the amount physically installed on the system. This extra memory is called virtual memory, and it is a section of a hard disk that's set up to emulate the computer's RAM. Virtual memory is a common technique used in a computer's operating system (OS).

Virtual memory uses both hardware and software to enable a computer to compensate for physical memory shortages, temporarily transferring data from RAM to disk storage. Mapping chunks of memory to disk files enables a computer to treat secondary memory as the main memory.

Virtual Memory vs Job Pool

Virtual memory is important for improving system performance and multitasking. The main advantage of this scheme is that programs can be larger than physical memory. However, users should not overly rely on virtual memory since it is considerably slower than RAM. If the OS swaps data between virtual memory and RAM too often, the computer will slow down. Virtual memory serves two purposes.

  1. It allows us to extend the use of physical memory by using the disk.
  2. And it allows us to have memory protection because each virtual address is translated to a physical address. Modern microprocessors intended for general-purpose use, a memory management unit, or MMU, is built into the hardware, and the MMU's job is to translate virtual addresses into physical addresses.

Benefits of Using Virtual Memory

Here are the following advantages or benefits of using virtual memory, such as:

  • It can handle twice as many addresses as the main memory.
  • It enables more applications to be used at once.
  • It frees applications from managing shared memory and saves users from adding memory modules when RAM space runs out.
  • It has increased speed when only a segment of a program is needed for execution.
  • It has increased security because of memory isolation.
  • It enables multiple larger applications to run simultaneously.
  • Allocating memory is relatively inexpensive.
  • It does not need external fragmentation.
  • CPU use is effective for managing logical partition workloads.
  • Data can be moved automatically.

What is Job Pool?

A job pool is a type of data structure in a batch processing system where various jobs are queued to be implemented when all the resources are made available. It decides which job will be executed next. The job pool contains both jobs that are currently executing and jobs that have been scheduled but are not yet being executed. When a job is executing, it is fully present in memory.

The main design is that whenever a new job is created, it is stored in the job pool, and when it becomes ready to be executed, it must be stored in the physical memory. But when a very large memory is required, only a part of the main memory gets executed while the remaining memory gets stored in the virtual memory.

Modern systems don't work this way. Computers that are big enough to run multiple tasks have a memory management unit that translates virtual memory addresses to physical addresses. And the operating system uses that to move each page between memory and disk this is called swapping or paging. This is an evolution from earlier multiprocessing systems. At first, processes were swapped as a whole. But nowadays, if there isn't enough memory to fit all currently running processes, the operating system can swap out the parts of processes that aren't currently being used.

Systems designed for large non-interactive computations generally use job management even today. Swapping takes time if the active processes require more memory than is available to run comfortably, which causes thrashing. To avoid this, job schedulers use job pools, arrange to start jobs, and possibly pause them based on available resources. The system works on top of an operating system based on virtual memory, so once a job is paused, it will naturally be swapped out as its pages in RAM are replaced by pages of active jobs.

Benefits of Using Job Pool

Here are the following benefits of using a job pool in an operating system, such as:

  • A job is a single unit that consists of a preset sequence of commands, data, and programs.
  • Processing takes place in the order in which they are received, i.e., first come, first serve, or according to the priority.
  • When a job is successfully run, the operating system releases its memory.
  • When a process is finished, the next job from the job spool is run without any user interaction.

Difference between Virtual Memory and Job Pool

The virtual memory and the job pool are used to store processes in a hard disk for some time and then later load them into the main memory.

Virtual Memory vs Job Pool

But they are different from each other in many ways, so below are the following differences between virtual memory and Job Pool such as:

Virtual Memory Job Pool
Virtual memory is a memory management technique that gives the users an illusion of infinite memory. Job pool is a program of the operating system located in the operating system and stores newly created processes while waiting for their respective resources.
Virtual memory represents the address generated by the CPU virtually. Job pool represents the pool from which the long-term scheduler chooses which job will be executed first.
A part of the process needs to be in memory for execution. A newly created process is stored here, waiting for required resources.
The concept behind virtual memory is that it creates an illusion that we are working with a very large memory when using only a part of it. The concept of the job pool states that a newly created process is stored in a pool called a job pool, where these processes wait for the resources to get allocated to get executed.
While loading processes from the hard disk to the main memory, virtual memory is not required if infinite memory is needed. While loading processes from the hard disk to the main memory, a job pool is always required to store a newly created process.

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