UNIX for Dummies Questions & Answers

Hi
Please can someone explain to me how they would go about monitoring the performance of a process in Unix. Lets say that a user is running a process in Unix but it seems to be taking a long time, whereas it completed a lot quicker yesterday. How would you go about investigating what is causing the process to run slower today in Unix?

The reason that I am confused is because there appears to be so many Unix commands that could be used when looking at performance issues. I am sure that you would use each Unix command for a specific reason but I want to know what you would do. Here are some commands that I know of:

Code:

ps -ef, top, du, ds, sar

Generally speaking, can you tell me what sequence of steps you would under take to understand why a process is running slowly and what Unix commands you would use to figure it out.

Many thanks

Usually I only use top.
Top will display a chart that is updated frequently (every second by default on my machine).
It gives the CPU usage, % used by the user, % by the system, and % idle.

In the chat it will tell you what % of the cpu each process is using, and how much processor time it has consumed up until that point (that is the 4th column named time). It also gives information on memory usage, current state, PID, user, and such.
It is a very useful utility and should get you what you need to know.

One thing to note that I have found with multicore processors. The % cpu use on each process is a % of a single core. Thus with a quad core you can have two processes using 100% and still have the total cpu use read as 50%.

Hope this helps.