A crash course in top

The top program is a text based application that displays a real-time summary of resource usage and a list of processes.
The on-screen display can be modified by issuing commands linked to keyboard keys

Type top to launch the program and try these common commands:
t
Toggles between text and graphical views of CPU usage (none, text, pipes, solid)
m
Toggles between text and graphical views of memory usage (none, text, pipes, solid)
E
Toggles unit size for memory (KiB through EiB)
1
[1] Shows CPU usage per core, while [2] shows per socket
c
Toggle COMMAND to/from executable vs full cmd line
d
Change refresh rate; Enter number in increments of .1 seconds
<
Change sort column one column to the left
>
Change sort column one column to the right
Note: it can be hard to detect which column is currently sorted
Recommend pressing [<] repeatedly to ensure sort order is left-most column
Then pressing [>] and counting off each Column
R
Toggle ascending/descending sort order of current column
↓
Scroll down through list of processes
↑
Scroll up through list of processes
→
Scroll right for information that runs offscreen
←
Scroll left to return from offscreen data
u
Filter by user; enter a username at the prompt
o
Filter by Other columns; COLUMN=pattern
=
Clear all column filters
h
Display an information dense cheat sheet of commands
W
Save configuration; applies current configuration on subsequent starts


Extended Topics
How to read graphical view of usage [Click To Expand]
In graphical mode CPU, RAM, & Swap are shown as:
%Cpu(s)
user%/sys%
total%
[|||||||
]
Unit Mem :
%used/amntM
 
[||||||||||
]
Unit Swap:
%used/amntS
 
[||||
]
 
user%
= Percentage of CPU used for user processes
 
sys%
= Percentage of CPU used for system processes
 
total%
= Percentage of CPU used for all processes
 
Unit
= The unit size for memory (i.e. GibiBytes)
 
%used
= Percentage of RAM/Swap used
 
amntM
= Amount of Memory(RAM) host has
 
amntS
= Amount of Swap space host has
How to Add, Remove, & Reorder columns [Click To Expand]
  • f
    Select Columns to Display, Hide, and Order
  •  
    To display or hide columns
  •  
    Asterix indicates displayed columns
  •  
    [Arrow Up/Down] to highlight a column
  •  
    [SPACE] to display/hide
  •  
    To change column order
  •  
    [Arrow Up/Down] to highlight a column
  •  
    [Arrow Right] to "pickup" the column
  •  
    Note how the highlight expands to the description
  •  
    [Arrow Up/Down] to move the column
  •  
    [Arrow Left] to "drop" the column into place
  •  
    To select the default column to sort on
  •  
    [Arrow Up/Down] to highlight a column
  •  
    [s] to select the highlighted column
  •  
    Note column name appears at end of very top line
  • ESC
    to exit Column Selection screen; Changes are applied instantly
    • Understanding Load Average [Click To Expand]
  •  
    * SkyView Perspective *
  •  
    Load average can be thought of as:
          "the number of cores needed to work on all running or waiting to be run tasks"
  •  
    When Load Average is _____ than the actual core count:
  •  
    less    = Good: there are unused resources
  •  
    equal  = Ok: all cores busy, no tasks waiting for a free core
  •  
    more  = Busy: all cores busy, tasks waiting for free cores
  •  
    The first line in top shows how the load is changing over time
  •  
    1st # = average load over last 1 minute
  •  
    2nd # = average load over last 5 minutes
  •  
    3rd # = average load over last 15 minutes