Quick and Easy Way to Monitor Process Memory Usage

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Whether you are a GNU/Linux sysadmin or desktop user, you might suspect a process of leaking memory, or be curious about just how much memory your biggest running processes are using. Most people know about the 'top' command, which gives a continuously updating display of all system processes, along with memory, swap and load usage. But sometimes you want to be able to see targeted process data, without a cluttered display. Here is a quick way to display process memory usage, sorted and limited to the top ten, using the 'ps' command:

ps ax -o rss,command | sort -nr | head -n 10

Here is what the output looks like:

serenity:~# ps ax -o rss,command | sort -nr | head -n 10 35936 spamd child 24556 SCREEN -dRRaAU 16340 emacs -nw 13568 /usr/sbin/apache2 -k start 13208 /usr/sbin/apache2 -k start 13176 /usr/sbin/apache2 -k start 13112 /usr/sbin/apache2 -k start 13108 /usr/sbin/apache2 -k start 13076 /usr/sbin/apache2 -k start 13016 /usr/sbin/apache2 -k start serenity:~#

This will show just the command name and resident set size (rss) in KB of a subset of system processes. The resident set size is the non-swapped physical memory used by each process, minus a small amount of overhead. So it will give you a decent idea of actual memory usage. The 'sort -nr' sorts the ps output numerically in reverse order (so the biggest memory hogs are at the top), and we limit the display to just the top ten. If you are maintaining a multi-user system, you can add the process owner data to the display:

ps ax -o rss,user,command | sort -nr | head -n 10

Which now looks like this:

serenity:~# ps ax -o rss,user,command | sort -nr | head -n 10 35936 root spamd child 24556 dmaxwell SCREEN -dRRaAU 16340 dmaxwell emacs -nw 13568 www-data /usr/sbin/apache2 -k start 13208 www-data /usr/sbin/apache2 -k start 13176 www-data /usr/sbin/apache2 -k start 13112 www-data /usr/sbin/apache2 -k start 13108 www-data /usr/sbin/apache2 -k start 13076 root /usr/sbin/apache2 -k start 13016 www-data /usr/sbin/apache2 -k start serenity:~#

To get a constantly updating display, use the 'watch' command and specify how often you would like it to update, in this case every 10 seconds:

watch -n 10 'ps ax -o rss,user,command | sort -nr | head -n 10'

This will clear your terminal and add a header line with the time interval, command name and a timestamp. Note that this works on any flavor of GNU/Linux as well as the various BSDs.

Every 10.0s: ps ax -o rss,user,command | sort -nr | head -n 10 Fri Mar 2 11:08:40 2012 35936 root spamd child 24556 dmaxwell SCREEN -dRRaAU 16340 dmaxwell emacs -nw 13568 www-data /usr/sbin/apache2 -k start 13208 www-data /usr/sbin/apache2 -k start 13176 www-data /usr/sbin/apache2 -k start 13112 www-data /usr/sbin/apache2 -k start 13108 www-data /usr/sbin/apache2 -k start 13076 root /usr/sbin/apache2 -k start 13016 www-data /usr/sbin/apache2 -k start