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Understanding the output of the TOP command

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TitleUnderstanding the output of the TOP command
Objective
To understand the output of the TOP command and adjust the columns accordingly.
Environment
  • EXOS
  • Linux based Appliances
Procedure
The following lists a description of the table columns seen in the output of the TOP command:

X670V-48x.1 # top
Mem: 390788K used, 630704K free, 0K shrd, 104084K buff, 69548K cached
CPU:  0.0% usr  9.0% sys  0.0% nic 90.9% idle  0.0% io  0.0% irq  0.0% sirq
Load average: 7.23 2.14 0.74 2/193 1749
  PID  PPID USER     STAT   RSS %MEM CPU %CPU COMMAND
 1239     2 root     SW<      0  0.0   0  6.0 [bcmLINK.0]
 1749  1748 root     R      676  0.0   1  3.0 top -d 3
 1436     1 root     S <  14460  1.4   1  0.0 ./hal
 1440     1 root     S    11400  1.1   1  0.0 ./cliMaster
 1535     1 root     S     5812  0.5   1  0.0 ./etmon
 1497     1 root     S     5280  0.5   1  0.0 ./dcbgp
 1446     1 root     S     4700  0.4   1  0.0 ./snmpSubagent
 1545     1 root     S     4640  0.4   0  0.0 ./xmld
 1444     1 root     S     4272  0.4   1  0.0 ./snmpMaster
 1581     1 root     S     4224  0.4   1  0.0 ./idMgr
 1432     1 root     S     3764  0.3   1  0.0 ./emsServer
 1491     1 root     S     3764  0.3   1  0.0 ./rtmgr update
 1493     1 root     S     3060  0.3   1  0.0 ./mcmgr
 1452     1 root     S     3036  0.3   1  0.0 ./fdb
 1450     1 root     S     3008  0.2   1  0.0 ./vlan
 1511     1 root     S     2980  0.2   1  0.0 ./pim
 1518     1 root     S     2692  0.2   1  0.0 ./acl
 1520     1 root     S     2692  0.2   1  0.0 ./netTools
 1503     1 root     S     2592  0.2   1  0.0 ./ospfv3
 1104     1 root     S     2588  0.2   1  0.0 /exos/bin/epm -t 40 -f /exos/confi

 
usr: user cpu time (or) % CPU time spent in user space
sys: system cpu time (or) % CPU time spent in kernel space
nic: user nice cpu time (or) % CPU time spent on low priority processes
idle: idle cpu time (or) % CPU time spent idle
irq: hardware irq (or) % CPU time spent servicing/handling hardware interrupts
sirq: software irq (or) % CPU time spent servicing/handling software interrupts

The load average is based on the CPU average for 1, 5, and 15 minute intervals.

PID (Process Identification) - The process ID assigned to each task. This is assigned a unique number which is not assigned in numerical order, so it is normal to what appears to be a random selection of numbers.

PPID (Parent Process Identification) - PIDs can share a single PPID. A single process can create several child processes. Typically a PPID of 1 will be seen within this column however other values will be seen depending on the parent process which it was derived from. This also indicates that the process was derived from the Init process which is also referred to the grandfarther process. The PID is unique whereas the PPID can be a duplicate value.

USER - The process or task in which user it was created under. Since EXOS runs on a Linux platform, the root user is used within the core background.

STAT (State) - Represent the state of the process/task running. The state flags include:
S - sleeping
D - uninterruptible sleep
R - running
W - swapped out process
Z - zombies
T - stopped or traced
N - process with positive nice value
< - process with negative nice value
 
RSS (Resident Set Size) - The amount of memory total used for the task/process used. This statistical information is also show in further detail within the command show memory process <name>.

%MEM - The share of physical memory in percentage being used by the process/task.

CPU - The physical processor being used. This can be represented by CPU0 or CPU1 depending on the CPU architecture type.

%CPU - The total CPU percentage in which is being used by the CPU. This is typical used to identify problematic process/tasks that could be overutilize the CPU.

COMMAND - Displays the command line and name used. This identifies the process and task used. processes without a command line (such as kernel threads) will be displayed in brackets.


In addition, the table format of the output can be sorted as follows by pressing the corresponding key:

P - Sort process list by CPU utilization
T - Sort process list by time usage
N - Sort process list by number (process ID)
M - Sort process list by memory usage
Additional notes
The TOP command output is somewhat limited compared to the TOP output on other Linux distributions. Other distributions will provide additional outputs and command syntax.

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