Using Tools and Utilities
The value of log files cannot be disputed, but log files do not complete the entire picture of system activity. There are many other activities and statistics that do not appear in log files, such as network utilization, open file count, memory use, CPU load, and more. Each of the components in a system affects the overall performance.
One of the most common components to monitor is CPU, with the primary question being “How busy is it?” There are actually two ways to view this. Contrary to many people’s view, CPU usage is a sign of a healthy system. CPUs should not sit idle. Typically, it is not so much the percentage of CPU usage that you should be worried about, but rather the load average.
That is not to say that percentage of CPU usage is not an important statistic. While a CPU should be in use, it should not be used needlessly.
Small, poorly planned applications, typically looping tightly in code, can drain a CPU, and those processes need to be identified.
top, CPU Percentage, and Load Averages
The first utility to reach for is top, a console-based (text) process monitor that will refresh its output and sort by various criteria. Its goal is to show you the “top” processes according to your sort. It does not give you every statistic possible, but understanding the data it presents is crucial to understanding what is happening with your system. The top utility will primarily display data about processes in user space. It also displays system CPU utilization and process 0 called kernel_task that gives information about the kernel.