Now lets suppose that we have a swapped application

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Now, let's suppose that we have a swapped application like app one here. And it suddenly needs to become active again. The user switches to it on the desktop. When this happens, we need to move itback into physical RAM. Now you might be asking, "Well why don't we just run it from the paging file on the hard disk drive?"Understand that even though the CPU does allow memory addresses to be mapped to a file on the hard disk. Anything running out of the paging file on the hard disk drive will do so very poorly if you try to use the paging file as if it were real RAM. And this is because hard disk drives transfer data much more slowly then physical RAM. So to keep the system running properly, the Windows kernel will try to find information associated with another process that isn't currently active. And then we'll swap that data to disk. So in this example app one needs to be actively processed. So the Windows kernel will identify that the information associated with app two really hasn't done anything for a long time. So it can be swapped out to disk. This frees up space in the physical RAM again for app one. So it swapped back into RAM and it becomes active. Disk Thrashing 3:38-4:28 Now as long as you don't over utilize the system RAM, virtual memory actually works really really well.However, you can have too much of a good thing. If too many applications are loaded on the system,performance is going to drop significantly. If the system has inadequate RAM installed, the CPU will spend all of its time constantly swapping data between the system RAM and the paging file on disk. This condition gets so bad that the CPUcan't perform any real useful work, instead all it does, is spend it's time swapping data back and forth,out of the paging file trying to free up enough physical RAM to keep the system running. When this happens we call it "disk thrashing". The hard disk light stays on constantly and the applications running on the system slow to a crawl. They may in fact appear to be totally hung. At very best they will respond very slowly when you try to use them. Addressing Disk Thrashing 4:29-4:51 In this situation you can take one of two actions to try to restore system performance. First of all, just unload some of those unnecessary applications on the system. If you can't, if they all have to be running then what you really need to do is add more physical RAM to the system. In fact, adding RAM to the system is probably one of the best options because it quickly and dramatically improves performance all the way around. Managing Virtual Memory on Windows 4:52-6:40 Now, you manage virtual memory settings on a Windows system by going into Control Panel and accessing your advanced system settings. Here you can adjust your page file settings. You can, for example, allow Windows to manage memory paging for you, which is the default setting. And usually this option works reasonably well, provides adequate performance. However if you're running many memory intensive applications you can manually specify the size of the paging file and when you do you can set an initial size, as well as a maximum size. And if you
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