4285ch02.fm Draft Document for Review May 4, 2007 11:35 am
58 Linux Performance and Tuning Guidelines
Figure 2-4 ethereal GUI
2.3.14 nmon
nmon, short for Nigel's Monitor, is a popular tool to monitor Linux systems performance
developed by Nigel Griffiths. Since nmon incorporates the performance information for
several subsystems, it can be used as a single source for performance monitoring. Some of
the tasks that can be achieved with nmon include processor utilization, memory utilization,
run queue information, disks I/O statistics, network I/O statistics, paging activity and process
metrics.
In order to run nmon, simply start the tool and select the subsystems of interest by typing their
one-key commands. For example, to get CPU, memory, and disk statistics, start nmon and
type c m d.
A very nice feature of nmon is the possibility to save performance statistics for later analysis in
a comma separated values (CSV) file. The CSV output of nmon can be imported into a
spreadsheet application in order to produce graphical reports. In order to do so nmon should
be started with the -f flag (see nmon -h for the details). For example running nmon for an
hour capturing data snapshots every 30 seconds would be achieved using the command in
Example 2-23 on page 59.