Resolving CPU bottlenecks

High CPU activity is normal and desirable. However, when a machine is 95 percent busy, we have to check if this is for all processors or if there is one processor that has a large load.

CPU % time is divided into 4 components:

Component	Name	Description
Us	User time	Time used by all user processes (non-kernel)
Sy	System	Time spent by operating system kernel
Id	Idle	Time spent idle
Wa	Wait	Time spent waiting for I/O

Getting ready

For this example, I compiled a C program named pos.exe. This program executes a SQL with a cartesian join to ensure that we have CPU activity for a while, so we have the time to track it down. You can open a command-line processor window and issue a SQL from there.

How to do it...

1. Get vmstat results. Issue the following command, and note the CPU columns on the right. In this example, the user CPU maintains a constant 90 percent or more activity, so immediate attention is required:

   [db2instp@nodedb21 ~]$ vmstat 5 100
   procs ----...