AIX 5L Problem Determination - IBM Redbooks

10.1.2 The vmstat command
The vmstat command reports statistics about kernel threads, virtual memory,
disks, traps, and CPU activity. Reports generated by the vmstat command can
be used to balance system load activity. These system-wide statistics (among all
processors) are calculated as averages for values expressed as percentages,
and as sums otherwise. For a CPU point of view, the highlighted two left-hand
columns and the four highlighted right-hand columns provide useful data, as
shown in the following example. The columns are discussed in the following
sections.
# vmstat 2
kthr memory page faults cpu
----- ----------- ------------------------ ------------ ----------r
b avm fre re pi po fr sr cy in sy cs us sy id wa
0 0 16998 14612 0 0 0 0 0 0 101 10 8 55 0 44 0
0 1 16998 14611 0 0 0 0 0 0 411 2199 54 0 0 99 0
0 1 16784 14850 0 0 0 0 0 0 412 120 51 0 0 99 0
0 1 16784 14850 0 0 0 0 0 0 412 88 50 0 0 99 0
The kthr columns
The kthr columns show how kernel threads are placed on various queues per
second over the sampling interval.
The r column
The r column shows the average number of kernel threads waiting on the run
queue per second. This field indicates the number of threads that can be run.
This value should be less than five for non-SMP systems. For SMP systems, this
value should be less than:
5 x (Ntotal - Nbind)
Where Ntotal stands for the total number of processors, and Nbind for the
number of processors that have been bound to processes, for example, with the
bindprocessor command.
If this number increases rapidly, examine the applications. However, some
systems may be running normally with 10 to 15 threads on their run queue,
depending on the thread tasks and the amount of time they run.
The b column
The b column shows the average number of kernel threads in the wait queue per
second. These threads are waiting for resources or I/O. Threads are also located
in the wait queue when waiting for one of their thread pages to be paged in. This
value is usually near zero. But, if the run-queue value increases, the wait queue
normally also increases. If processes are suspended due to memory load
238 IBM ^ Certification Study Guide - AIX 5L Problem Determination Tools and Techniques