nmon displays the performance stats on-screen in a condensed format or b) the same stats are saved to a comma-separated values data file for later graphing and analysis to aid the understanding of computer resource use, tuning options and bottlenecks.
To start collecting the stats to a file use the -f or -F option
When viewing in on-screen mode the stats displayed are controlled by the user using single letter toggles. For example, "c" to show CPU and then another "c" will switch the CPU stats off. Use h to display a list of the options. When saving the stats to a file, there is a common default set of stats and then users can request more using command line options. Use nmon -? to display all the options. The saved file is in a comma separated values format with a simple for later processing and graphing.
Later a version was written for the Linux operating system running on IA-32, x86, x86_64, IBM RS/6000 and POWER processors, Mainframe and ARM. nmon for Linux was released by IBM to open-source in July 2009. The code is available from the Sourceforge open source repository.
The nmon for AIX code was later bundled in as part of the AIX operating systems. From AIX 5.3 TL09 and AIX 6.1 TL02 onward it was included in the default installation of AIX and fully supported by IBM. The nmon command and the topas command are the same binary but behave differently depending on the command name used. Users can switch between topas mode and nmon mode with the tilde key.
The two editions have completely different source code but offer many similar features, command line options and data — as much as the underlying operating system allow. nmon is used by AIX and Linux Systems Administrators and performance tuning specialists around the world. There have been 600,000 downloads of nmon for Linux from SourceForge, showing it popularity and it is found in Linux operating System Repositories.
Features
There are two runtime modes available:
In Online Mode it uses curses for efficient screen handling, which updates the terminal frequently for real-time monitoring.
In Capture Mode, the data is saved to a file in CSV format for later processing and graphing. The file also includes important configuration details that are useful for recommending tuning.
nmon concentrates on performance information for the performance tuner and in a concise layout to aid understanding. This includes CPU, memory, disks, adapters, networks, NFS, Kernel statistics, File-systems, Workload Manager, Workload Partitions and Top Processes.
nmon includes support for older AIX releases, Linux running on x86, POWER and Mainframe platforms and other Linux supporting hardware.
Screenshots
Alternatives
On AIX, there is the topas command that can output reports to a file but this is not in a format that can be used easily as a source for a spread sheet or web tools like rrdtool. On Linux, there is the top command which is good for CPU and processes but does not cover disks and networks. For disk I/O, the iostat command can give you the details and ntop for network information. But neither of these commands allow saving data in a format suitable for a spreadsheet or simple further processing. Linux utility dstat can be used to produce text data, even in comma separated value format, which is quite suitable for spreadsheet programs.
