htop

• Linux Memory and Processes

htop is an alternative display for top, showing system processes.

By default, htop will order the processes by PID.

echo linproc /compat/linux/proc linprocfs rw 0 0 >> /etc/fstab
mkdir -p /usr/compat/linux/proc
ln -s /usr/compat /compat
mount linproc

Show processes being run by user mysql:

htop -u mysql

Display threads for user apache, sorted by how long they have been running:

htop -u apache --sort-key TIME

See how much memory apache threads are really using, highest values first:

htop -u apache --sort-key M_RESIDENT

Watching the system to see what programs are using the most memory, the highest percentage of CPU, the highest percentage of memory, and then running the longest time:

htop -u apache --sort-key M_RESIDENT
htop -u apache --sort-key PERCENT_CPU
htop -u apache --sort-key PERCENT_MEM
htop -u apache --sort-key TIME

The default values displayed are:

• PID
• USER
• PRIORITY
• NICE
• M_SIZE
• M_RESIDENT
• M_SHARE
• STATE
• PERCENT_CPU
• PERCENT_MEM
• TIME
• Command

htop's argument for sorting by keys is not consistent across versions, despite what the –help output may say. To sort by a key, use –sort-key <value>, which will work everywhere.