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Installation

The Swap Partition

Linux systems typically use a partition as swap space. This is where unused

items taking up space in memory are placed until they are needed again so that

the memory they are using can be used for something else. Other operating

systems use a file on the file system for this purpose, and while Linux can

be set up to do the same thing it is typically set up to use a swap partition

because it is faster and isolated from the rest of the file systems.

You can't have too much swap space. Although excessive swap space may

amount to wasted resources, it will not cause the system to exhibit thrashing

or otherwise cause operational problems. It simply will not get used unless

memory usage escalates.

Note:

Thrashing   When the operating system spends most of its

time paging real memory in and out of the swap space it is

said to be  thrashing  and no useful work gets done. This can

happen for a variety of reasons. On another operating system,

larger than  optimum  swap space would quickly drive the

system into thrashing. Deciding the amount of RAM that

will be swapped out based on the size of swap space causes

 all  pages to be swapped out immediately after they are

used and the machine spends all its time moving pages in

and out of memory and never gets anything done. (Well,

at least it seems like it) The more reasoned approach is to

base swapping activity on the age of the unused page and

the amount of free memory. As the amount of free memory

decreases, pages get swapped at an earlier age. This can

still be made to thrash if placed under enough load. With

many processes allocating and using many buffers, memory

can fill up faster than it can be swapped out. The end result

is either machine lockup because of exhausted memory or it

begins thrashing when the swap age gets to zero.