Page 40 - DCAP106_OPERATING_SYSTEM_TOOLS

Unit 2: Red Hat Linux 9 Basics

Notes

Notes Actually, Swap memory is not a memory in the conventional sense. It is a disk space
which is used by the operating system in order to store information for the time being.

The Use of Load Average to Measure CPU Usage

The CPU usage, in case of Linux as well as other UNIX-based operating systems, is frequently
assessed in terms of load average. We can display Load average by making use of three numerical
values. The load average is defined as the average number of processes which are waiting to be
executed system over a specified time interval. The load average can be examined in different
manners.

Example: We can examine the contents of the file /proc/loadavg.
Here, the first three figures (0.44, 0.29, 0.17) depict the system’s load average taken over the last
one, five, and fifteen minutes.
The output of this program also displays the total time for which the computer has been running.
The top program can be executed. This program displays a wealth of information. Also, the
display updates itself in every few seconds.
Note that the first part depicts the load average of the system, and the usage of memory in the
system. The remaining display demonstrates the processes running on the system, together with
a wealth of information on every process.
This output allows you to change many properties of the display and even to destroy processes.
In order to exit the top display, it is required to press q on the keyboard.

Memory-related Information

To determine information regarding the total amount of RAM in the system and the amount of
swap memory, we can look at the System Monitor dialog. Another quick option for determining
the status of RAM and swap is to display the contents of the file /proc/meminfo. This is shown
as below:
Figure 2.15: Example of Command /proc/meminfo

Source: http://superuser.com/questions/521551/cat-proc-meminfo-what-do-all-those-numbers-mean
We can also examine the usage of memory via the System Monitor or the top program.

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