Chapter 2. Resource Monitoring

23

procs

memory

swap

io

system

cpu

r

b

w

swpd

free

buff

cache

si

so

bi

bo

in

cs

us

sy

id

1

0

0

0 524684 155252 338068

0

0

1

6

111

114

10

3

87

The process related fields are:

  r

  The number of runnable processes waiting for access to the CPU

  b

  The number of processes in an uninterruptible sleep state

  w

  The number of processes swapped out, but runnable

The memory related fields are:

  swpd

  The amount of virtual memory used

  free

  The amount of free memory

  buff

  The amount of memory used for buffers

  cache

  The amount of memory used as page cache

The swap related fields are:

  si

  The amount of memory swapped in from disk

  so

  The amount of memory swapped out to disk

The I/O related fields are:

  bi

  Blocks sent to a block device

  bo

  Blocks received from a block device

The system related fields are:

  in

  The number of interrupts per second

  cs

  The number of context switches per second

The CPU related fields are:

  us

  The percentage of the time the CPU ran user level code

  sy

  The percentage of the time the CPU ran system level code

  id

  The percentage of the time the CPU was idle

When

vmstat

is run without any options, only one line is displayed. This line contains averages,

calculated from the time the system was last booted.

However, most system administrators do not rely on the data in this line, as the time over which it

was collected varies. Instead, most administrators take advantage of

vmstat

's ability to repetitively

display resource utilization data at set intervals. For example, the command

vmstat 1

displays one

new line of utilization data every second, while the command

vmstat 1 10

displays one new line

per second, but only for the next ten seconds.

In the hands of an experienced administrator,

vmstat

can be used to quickly determine resource

utilization and performance issues. But to gain more insight into those issues, a different kind of tool

is required   a tool capable of more in depth data collection and analysis.