Chapter 2. Resource Monitoring

21

Tip

A better solution than using free  s would be to run free using the watch command. For example,

to display memory utilization every two seconds (the default display interval), use this command:

watch free

The watch command issues the free command every two seconds, after first clearing the screen.

This makes it much easier to see how memory utilization changes over time, as it is not necessary to

scan continually scrolling output. You can control the delay between updates by using the  n option,

and can cause any changes between updates to be highlighted by using the  d option, as in the

following command:

watch  n 1  d free

For more information, refer to the watch man page.

The watch command runs until interrupted with [Ctrl] [C]. The watch command is something to keep

in mind; it can come in handy in many situations.

2.5.2.

top

While

free

displays only memory related information, the

top

command does a little bit of every 

thing. CPU utilization, process statistics, memory utilization  

top

does it all. In addition, unlike

the

free

command,

top

's default behavior is to run continuously; there is no need to use the

watch

command. Here is a sample display:

11:13am

up 1 day, 31 min,

5 users,

load average: 0.00, 0.05, 0.07

89 processes: 85 sleeping, 3 running, 1 zombie, 0 stopped

CPU states:

0.5% user,

0.7% system,

0.0% nice, 98.6% idle

Mem:

255508K av, 241204K used,

14304K free,

0K shrd,

16604K buff

Swap: 530136K av,

56964K used, 473172K free

64724K cached

PID USER

PRI

NI

SIZE

RSS SHARE STAT %CPU %MEM

TIME COMMAND

8532 ed

16

0

1156 1156

912 R

0.5

0.4

0:11 top

1520 ed

15

0

4084 3524

2752 S

0.3

1.3

0:00 gnome terminal

1481 ed

15

0

3716 3280

2736 R

0.1

1.2

0:01 gnome terminal

1560 ed

15

0 11216

10M

4256 S

0.1

4.2

0:18 emacs

1 root

15

0

472

432

416 S

0.0

0.1

0:04 init

2 root

15

0

0

0

0 SW

0.0

0.0

0:00 keventd

3 root

15

0

0

0

0 SW

0.0

0.0

0:00 kapmd

4 root

34

19

0

0

0 SWN

0.0

0.0

0:00 ksoftirqd_CPU0

5 root

15

0

0

0

0 SW

0.0

0.0

0:00 kswapd

6 root

25

0

0

0

0 SW

0.0

0.0

0:00 bdflush

7 root

15

0

0

0

0 SW

0.0

0.0

0:00 kupdated

8 root

25

0

0

0

0 SW

0.0

0.0

0:00 mdrecoveryd

12 root

15

0

0

0

0 SW

0.0

0.0

0:00 kjournald

91 root

16

0

0

0

0 SW

0.0

0.0

0:00 khubd

185 root

15

0

0

0

0 SW

0.0

0.0

0:00 kjournald

186 root

15

0

0

0

0 SW

0.0

0.0

0:00 kjournald

576 root

15

0

712

632

612 S

0.0

0.2

0:00 dhcpcd

The display is divided into two sections. The top section contains information related to overall system

status   uptime, load average, process counts, CPU status, and utilization statistics for both memory

and swap space. The lower section displays process level statistics, the exact nature of which can be

controlled while

top

is running.