Virtual Memory vs Page File

Virtual Memory vs Page File

Using virtual memory is a common approach to operating systems. This is because it provides a lot of advantages at low cost. As you know each computer has a memory (RAM), which have all running programs. Each process takes their part of the memory and if you open too many programs it can do. Here comes the virtual memory support.

By using virtual memory, regular parts of your RAM that you have not used recently are recorded on the hard disk. Thus frees up space in RAM memory for new programs. The transfer of parts from memory and recording them on the hard disk automatically and is managed by the operating system. Thanks to virtual memory, you have a lot more memory than as your real RAM. Obtained much more efficient use of RAM, only the most accessible parts of it actually remains on it and transfer of unused hard disk. If a process is requested information located on the hard disk, it is transferred to memory. If no empty memory, the portion of employees transferred to the hard disk.

What is Page file (page file)?

The hard disk where this information is recorded is called the Page file (page file). The name comes from the word page (page). When using virtual memory, real memory is divided into equal-sized sections called pages. These are pieces of information to be transferred. The idea of ??virtual memory is that each program thinks it has more memory than it actually is free. Use virtual addresses that are different from the real addresses in memory. Thus two different processes can operate with the same virtual addresses. Later they are converted to different real addresses. That is, the programs work with virtual addresses and real hardware. To convert a virtual address is used in a real page table (page table). This table contains information that associates each virtual page and address in real memory or address in the Page file (page file).

Where should be the Page file (page file)?

For faster operation of virtual memory Page file should be readily accessed by the head of the hard disk. If you have one hard drive, place the file in the Page Title, which has the most activity, ie they are installed programs. There is the chance for a head on the hard disk most of the time. If you have more than one hard disk, place the file in the Page in which no operating system is installed and in which there is not much activity. Thus, where once the file is accessible chapters of this hard drive will remain there and are ready to access it quickly.

What should be the size of the Page File?

It is often debated question. Unfortunately the answer is very simple and unambiguous. Many times I’ve seen it recommended size is 1.5 or 2 times the amount of RAM. Also minimum and maximum sizes are the same so as not to delay receiving a change of its size.

If you follow these recommendations should I set my Page file (page file) is always 3GB. This is not the best solution. The minimum size it is better to be as much as normal its usability. Look in Task Manager-a and see how, in normal operation as above is its size. This is the value that will ensure that there is constantly increasing and decreasing. Maximum size is no longer a problem to be quite large value, provided that you have hard disk space. For example I have 1.5GB RAM memory, and looked the size of the Page file is currently about 400 – 500MB. I opened the browser, antivirus, Skype and a few small programs which are generally open, plus a working program. Overall, this is the most frequent state of my computer. I think I set a minimum size Page file (page file) 500MB, but because I have plenty of room to set maximum size 2GB. These 2GB plus my 1.5GB RAM memory to me quite enough, at least in Windows XP. Naturally it will be even better if I have more RAM, then you will use even less virtual memory. If your computer using multiple user accounts and switch between accounts remain many programs included, you will probably need a bigger Paige file.

Disadvantages of virtual memory

Disadvantages of virtual memory are mainly two. The first is that the Page file takes up space on your hard disk. That is almost no problem, unless your drive has a small capacity. The second and major disadvantage is connected with the speed of the disk. While RAM is fast enough, we can not say the same for hard drives. His speed read / write is quite low and it greatly reduces performance when using virtual memory. If a computer has less RAM, it is increasingly relying on virtual. So he often exchanges information with the Page file and it is felt by a significant delay in the work. If enough RAM, almost no delay due to virtual memory.

History of virtual memory

In the 40's and 50's of the 20th century, before the introduction of virtual memory, larger programs themselves have served its function. They have guided the transfer of information between primary and secondary storage device and vice versa (from RAM to the hard disk and vice versa). This is one of the reasons for the introduction of virtual memory – to ease developers in making these programs. Virtual memory was developed in the period around 1959-1962 year. Naturally there was a lot of problems and disputes related thereto. For example the need for complicated and expensive hardware and the oppression of experts that the technology will be much less effective than previous similar technologies. In 1969 Division reversed and it began to be applied in commercial products. The first one computer is using virtual memory NORD-1. Originally used segment separation of memory and later pagination (paging).

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