Each process running inside the machine ocupies small or large part of memory, the CPU routes the active process within the so named memory allocated, distributing or simply stacking it.
The stack used for process management stack on each other all the application processes called each time one after the other until all the RAM, the RAM once the processes are channeled in the swaps with the same system of stacking up to its complete saturation. What happen if the swap is completed? When the swap is full of active processes, our operative system will no longer be able to process anything else, the system will block active application that we will open, it will slows down untill its complete block forced you to restart to resume your activity.
The Windows operative system is structured so that the stack memory processes running one after another in the stack and that the CPU sends signals of activity to each process loaded in the stack and swap so activating the loading of each process in the memory. This methodology uses an excessive memory, because the CPU doesn't send signal only to active processes but to all loaded in succession.
On a Unix or Unix Like system, the processesare distributed equally between swap and allocated memory, the CPU sends the signal in a orderly manner but not as invasive as in Windows System, using each active process as a block help the whole system so that the active processes are handledbest by the CPU which sends signal accurate and fast to every process of the stack and the swap alternating instead letting slide the array, so the operating system is less stressed than that used Windows system. Diversification or processes and the manage to boost Unix system than Windows repetitive makes the OS more malleable and less stressed.
Another difference between the two system is the management of the stack. On Windows system when an application is closed automatically match of this trial on the stack is deleted, because no longer exist but the stack leaving a hole in the middle between a process and another. This way of handling stack can create overflow issue; in fact, just a trojan infect the system that the hole left open in the stack from the closure of the various application because this repeats itself endlessy and blocks the whole system to increase dizzying memory.
If, for example, there are stored in the memory four processes each comprising 20 megabyte of the stack and it's eliminated the process number 3 leave free 20 megabyte, on Windows system, the hole will not be replaced by 4,but will leave a hole to be replaced by the next application, if the application will have a mass of less of 20 megabyte active memory called the program will not have problems whatsoever, but if you need more than 20 megabytes to boot and work may be a slight delay or block the new application, in Similarly, if a trojan or malware, screw you install the operating system they occupy that part of memory (even minimal) which was vacated and replicate indefinitely obstruct not only the RAM but also swap.
On Unix and Unix Like system when an application is closed that is among other, the processes on the stack not leave the hole until it will replace from another application, but will slide up the processes to close the hole created by the application that there is more, this mean that it will have less chance to create overflow problems as for other application activate after as for trojan or malware installed on the machine.
The swap creates a plunger between the RAM and the operative system so that new technologies and programs that take up always more memory don't block constantly the system while they work. It's must always necessary use the swap to prevent any kind of detention by the system and to avoid to confuse a lacking memory block with an infection informatic.
Especially when you surf in internet, in facts any open windows browser is equivalent to an active process in memory, each times that the page laods itself occupies another space in the memory as a separate process, even if it is not a job large scale. Each tab within each open browser window does not imply more active memory on the stack, but simply a more solid network adapter.
In which case you use an operative system purely as a server the swap is necessary for the perfect manage of all clients, even if you use few applications and with a low use of memory, the events of each application in any client in the network, that sometimes can be of a large footprint, even if the client don't introduce additional memory to their application on the server but implies an increase in memory on the server when using internet or intranet, as for the mail as for the applications work in common with other offices, the control programs used by system administration using a large memory allocated to being able to work properly and without wasting memory.
If the system in the absence of a swap must overwork the memory and the stack it's probable that the discs will be broken much fast than in the disk is present a swap as it is regurarly.
If the Windows system the swap is created automatically to each reboot, in the Unix system is not quite so elementary, it's possible choose during the formatting the quantity of disk dedicated to the swap, if you choose to don't have a swap, to insert it will be necessary a new partitioning of the disk.
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pubblicato il 27/08/2010