Process:
A process is an instance of a computer program that is
being executed. It contains the program code and its
current activity. In another word, a process is an
operating system level concept used to describe a set of
resources (such as external code, libraries and primary
thread) and the necessary memory allocations used by a
running application. For each *.exe loaded into memory,
the OS creates a separate and isolated process for use
during its life time [1, 2].
Virtual
Memory:
Virtual memory is a common part of most operating
systems on desktop computers. It has become so common
because it provides a big benefit for users at a very
low cost. Most computers today have something
like 32 or 64 megabytes of RAM available for the CPU to
use. Unfortunately, that amount of RAM is not enough to
run all of the programs that most users expect to run at
once.For
example, if you load the operating system, an e-mail
program, a Web browser and word processor into RAM
simultaneously, 32 megabytes is not enough to hold it
all. If there were no such thing as virtual memory, then
once you filled up the available RAM your computer would
have to say, "Sorry, you can not load any more
applications. Please close another application to load a
new one." With virtual memory, what the computer can do
is look at RAM for areas that have not been used
recently and copy them onto the hard disk. This frees up
space in RAM to load the new application .The area of
the hard disk that stores the RAM image is called a page
file. It holds pages of RAM on the hard disk, and the
operating system moves data back and forth between the
page file and RAM. On a Windows machine, page files have
a .SWP extension [3].
Working Set:
Working set is the set of memory pages that have been
recently touched by a program. At this point these 10
pages are added to the working set of the process. If
the process then goes and copies this data into another
10 MB cache previously allocated, everything else
remains the same but the Working Set goes up again by 10
Mb if those old pages where not in the working set. But
if those pages where already in the working set, then
everything is good and the programs working set remains
the same.
Memory Usage:
Mem Usage is the working set size, not its total virtual
memory usage. It is the amount of physical memory which
is directly (currently) allocated to the process. It can
be accessed without causing a page fault. This includes
pages shared with other processes [4]. |
