Use the vmstat command to determine where the system performance problems are. vmstat reports statistics about kernel threads, virtual memory, disks, and CPU activity.

Here is the syntax for the vmstat command:

vmstat [-fskIt] [drives] [interval [count]]
Hard drives to monitor (hdisk0, hdisk1, and so on).
The update period. If vmstat is run without an interval, it shows the statistics from reboot. If an interval is set, the first line is the statistics since the system startup, and the next lines show the statistics from the previous line.
Number of iterations.

Reports from vmstat Command
Forks report: Number of forks since the last system startup. vmstat -f
Interrupts report: The example shows an interrupts report with a delay of two seconds, three times. vmstat -i <interval> <count>vmstat -i 2 3
Sum structure report: The absolute count of paging events since system initialization. vmstat -s
I/O activity: The example shows an I/O report taken every two seconds 10 times with time stamps included. vmstat -Ivmstat-It 2 10
Time stamps: The -t option gives time stamps on each line of data. This is useful analyzing data. vmstat -t <interval> <count>