40

Chapter 3. Bandwidth and Processing Power

The statistics contained in this report are no different from those produced by many of the other tools.

The biggest benefit here is that

sar

makes the data available on an ongoing basis and is therefore

more useful for obtaining long term averages, or for the production of CPU utilization graphs.

On multiprocessor systems, the

sar  U

command can produce statistics for an individual processor

or for all processors. Here is an example of output from

sar  U ALL

:

Linux 2.4.18 14smp (falcon.example.com)

12/16/2002

12:00:01 AM

CPU

%user

%nice

%system

%idle

12:10:00 AM

0

3.46

21.47

1.09

73.98

12:10:00 AM

1

3.91

18.73

1.03

76.33

12:20:01 AM

0

1.63

0.25

0.78

97.34

12:20:01 AM

1

1.82

0.20

0.81

97.17

...

10:00:00 AM

0

39.12

0.75

1.04

59.09

10:00:00 AM

1

31.22

0.92

1.09

66.77

Average:

0

7.61

4.91

3.86

83.61

Average:

1

7.33

4.78

3.88

84.02

The

sar  w

command reports on the number of context switches per second, making it possible to

gain additional insight in where CPU cycles are being spent:

Linux 2.4.18 14smp (falcon.example.com)

12/16/2002

12:00:01 AM

cswch/s

12:10:00 AM

537.97

12:20:01 AM

339.43

...

10:10:00 AM

319.42

Average:

1158.25

It is also possible to produce two different

sar

reports on interrupt activity. The first, (produced using

the

sar  I SUM

command) displays a single "interrupts per second" statistic:

Linux 2.4.18 14smp (falcon.example.com)

12/16/2002

12:00:01 AM

INTR

intr/s

12:10:00 AM

sum

539.15

12:20:01 AM

sum

539.49

...

10:40:01 AM

sum

539.10

Average:

sum

541.00

By using the command

sar  I PROC

, it is possible to break down interrupt activity by processor (on

multiprocessor systems) and by interrupt level (from 0 to 15):

Linux 2.4.18 18.8.0 (pigdog.example.com)

12/16/2002

12:00:00 AM

CPU

i000/s

i001/s

i002/s

i008/s

i009/s

i011/s

i012/s

12:10:01 AM

0

512.01

0.00

0.00

0.00

3.44

0.00

0.00

12:10:01 AM

CPU

i000/s

i001/s

i002/s

i008/s

i009/s

i011/s

i012/s

12:20:01 AM

0

512.00

0.00

0.00

0.00

3.73

0.00

0.00

...

10:30:01 AM

CPU

i000/s

i001/s

i002/s

i003/s

i008/s

i009/s

i010/s

10:40:02 AM

0

512.00

1.67

0.00

0.00

0.00

15.08

0.00

Average:

0

512.00

0.42

0.00

N/A

0.00

6.03

N/A