It can display system summary information as well as a list of processes or threads currently being managed by the Linux kernel. The top program provides a dynamic real-time view of a running system. If you want to make top a bit more memory-friendly, issue the command top -o %MEM, which will cause top to sort all processes by memory used (see figure below). %MEM - Memory Usage (RES): A task’s currently used share of available physical memory.In a true SMP environment, if a process is multi-threaded and top is not operating in Threads mode, amounts greater than 100% may be reported.

%CPU - CPU Usage: The task’s share of the elapsed CPU time since the last screen update, expressed as a percentage of total CPU time.Two of the most important factors displayed by the top command are: The top command provides a limited interactive interface for process manipulation as well as a much more extensive interface for personal configuration. Note that the data is continuously updated and top command details the processes in real-time. The top command displays information about:

Ubuntu see cpu usage