Thursday, 7 May 2015

Understanding TOP Command

If you see the above snapshot taken of the TOP command, then lets understand this whole output and interpretation of TOP command in below notes :-


This first line indicates in order:

current time (15:00:52)
uptime of the machine (up 41 min)
users sessions logged in (6 users)
average load on the system (load average: 1.20, 0.33,0.12) the 3 values refer to the last minute, five minutes and 15 minutes.


The second row gives the following information:

Processes running in totals (178 total)
Processes running (4 running)
Processes sleeping (174 sleeping)
Processes stopped (0 stopped)
Processes waiting to be stoppati from the parent process (0 zombie)


The third line indicates how the cpu is used. If you sum up all the percentages the total will be 100% of the cpu. Let’s see what these values indicate in order:

Percentage of the CPU for user processes (90.3%us)
Percentage of the CPU for system processes (9.7%sy)
Percentage of the CPU processes with priority upgrade nice (0.0%ni)
Percentage of the CPU not used (0.0%id)
Percentage of the CPU processes waiting for I/O operations(0.0%wa)
Percentage of the CPU serving hardware interrupts (0.0% hi — Hardware IRQ
Percentage of the CPU serving software interrupts (0.0% si — Software Interrupts
The amount of CPU ‘stolen’ from this virtual machine by the hypervisor for other tasks (such as running another virtual machine) this will be 0 on desktop and server without Virtual machine. (0.0%st — Steal Time)

Now the memory usage

The fourth and fifth rows respectively indicate the use of physical memory (RAM) and swap. In this order: Total memory in use, free, buffers cached. On this topic you can also read the following article

Now the Processes list

And as last thing ordered by CPU usage (as default) there are the processes currently in use. Let’s see what information we can get in the different columns:

PID – l’ID of the process(5016)
USER – The user that is the owner of the process (oracle)
PR – priority of the process (20)
NI – The “NICE” value of the process (0)
VIRT – virtual memory used by the process (287m)
RES – physical memory used from the process (21m)
SHR – shared memory of the process (8888)
S – indicates the status of the process: S=sleep R=running Z=zombie (S)
%CPU – This is the percentage of CPU used by this process (38.9)
%MEM – This is the percentage of RAM used by the process (0.5)
TIME+ –This is the total time of activity of this process (0:52.84)
COMMAND – And this is the name of the process (gnome-terminal)

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