Top is an utility provided by Linux. It gives completes analysis of all the process running in the system like all the active process. Also it tells about system performance like CPU, Memory utilisation. Some of the commands are:
shift + M - List process according to memory usage
shift + P - List the process according to CPU usage
Shift + W - For saving top output to a file.
EXAMPLE:
top - 04:38:00 up 10 days, 13:23, 1 user, load average: 0.00, 0.01, 0.05
Tasks: 90 total, 2 running, 88 sleeping, 0 stopped, 0 zombie
%Cpu(s): 0.0 us, 0.0 sy, 0.0 ni,100.0 id, 0.0 wa, 0.0 hi, 0.0 si, 0.0 st
KiB Mem : 1014976 total, 116512 free, 93008 used, 805456 buff/cache
KiB Swap: 0 total, 0 free, 0 used. 628588 avail Mem
PID USER PR NI VIRT RES SHR S %CPU %MEM TIME+ COMMAND
14446 postgres 20 0 279896 2236 1472 S 0.3 0.2 5:04.70 postgres
1 root 20 0 128092 6700 3944 S 0.0 0.7 0:27.88 systemd
2 root 20 0 0 0 0 S 0.0 0.0 0:00.10 kthreadd
3 root 20 0 0 0 0 S 0.0 0.0 0:01.29 ksoftirqd/0
7 root rt 0 0 0 0 S 0.0 0.0 0:00.00 migration/0
8 root 20 0 0 0 0 S 0.0 0.0 0:00.00 rcu_bh
9 root 20 0 0 0 0 R 0.0 0.0 1:26.88 rcu_sched
10 root rt 0 0 0 0 S 0.0 0.0 0:03.87 watchdog/0
12 root 0 -20 0 0 0 S 0.0 0.0 0:00.00 khelper
13 root 20 0 0 0 0 S 0.0 0.0 0:00.00 kdevtmpfs
14 root 0 -20 0 0 0 S 0.0 0.0 0:00.00 netns
15 root 20 0 0 0 0 S 0.0 0.0 0:00.01 xenwatch
16 root 20 0 0 0 0 S 0.0 0.0 0:00.00 xenbus
18 root 20 0 0 0 0 S 0.0 0.0 0:00.14 khungtaskd
19 root 0 -20 0 0 0 S 0.0 0.0 0:00.00 writeback
20 root 0 -20 0 0 0 S 0.0 0.0 0:00.00 kintegrityd
21 root 0 -20 0 0 0 S 0.0 0.0 0:00.00 bioset
22 root 0 -20 0 0 0 S 0.0 0.0 0:00.00 kblockd
23 root 0 -20 0 0 0 S 0.0 0.0 0:00.00 md
28 root 20 0 0 0 0 S 0.0 0.0 0:00.24 kswapd0
29 root 25 5 0 0 0 S 0.0 0.0 0:00.00 ksmd
Below are the few description of the contents of TOP Command:
Job - Present time, how much time system is up, how many users connected, load average.
Task - How many total tasks, how many tasks running, how many tasks sleeping, how many tasks stopped, how many zombie process.
CPU - % of CPU used by users, % of CPU used by system, % of CPU used by nice value, idle CPU %, % of CPU wating for IO(to write), % of CPU used by Hardware Interupt, % of CPU used by Software Interupt, Steal time - used when there is a virtual box( delay in getting the actual CPU by virtual CPU in virtual systems)
Memory - Total RAM, Memory Used (Actually used - buffer), Memory Free( Actual + buffer + cache from swap) , Buffer( when system have free memory, it extracts few pages and keep it in buffer for caching, if system needs, it will give back the pages from buffer)
Swap- Total Swap, Swap Used, free, caching
PID - Process ID
USER - user through which process are running
PR - Priority - Process priority. 0 - highest priority 40 - Lowest
NI - Nice value - CPU Scheduling Priority. Utility through which we can set the priority manually. -19 -highest priority 20 - lowest priority
Virtual Memory - Each process cant access direct physical memory, so it uses virtual memory. Each process have its own virtual space. Physical memory address space is mapped to virtual memory address space. It is sort of security restriction where process cant directly indulge with Physical RAM. MMU - Memory Management Unit does the mapping between physical address space to virtual address space. pmap 1 shows mapping between VAS to PAS.
Resident Memory - Total Physical Memory that is non swapped.
Shared Memory - Memory that is being shared by other processes
S - state - Sleeping or running
% CPU - % of CPU used by the process
% MEM - % of Memory Used by the process
Time - How long is the process running
Command - What is the command that is being executed.
C - Process with obsolete path
k <pid> - to kill a process
z - Change color of top
r - for re nice a value
1 - shows the number of CPU
d - change refresh rate - Default 3 sec
A - Splits screen into multiple part/screen. Top Right Side says which split screen I am. So accordingly we can sort per split screen. Goto different split screen using a. Shift + a will toggle screen from small to big.
h - help
n - Reduce the number of listed process to n
I - To hide load average line
t - to hide CPU states. 2nd and 3rd line.
m - to hide/show the memory line. 4th and 5th.
top -u postgres or top and press u
top -n 2 stops refresh after 2 sec
top -p pid, pid
top -b -n 1
top -d3 -b -n 2 > top_output.txt.
top -H -p pid
Shift F - add extra column as required.
shift + M - List process according to memory usage
shift + P - List the process according to CPU usage
Shift + W - For saving top output to a file.
EXAMPLE:
top - 04:38:00 up 10 days, 13:23, 1 user, load average: 0.00, 0.01, 0.05
Tasks: 90 total, 2 running, 88 sleeping, 0 stopped, 0 zombie
%Cpu(s): 0.0 us, 0.0 sy, 0.0 ni,100.0 id, 0.0 wa, 0.0 hi, 0.0 si, 0.0 st
KiB Mem : 1014976 total, 116512 free, 93008 used, 805456 buff/cache
KiB Swap: 0 total, 0 free, 0 used. 628588 avail Mem
PID USER PR NI VIRT RES SHR S %CPU %MEM TIME+ COMMAND
14446 postgres 20 0 279896 2236 1472 S 0.3 0.2 5:04.70 postgres
1 root 20 0 128092 6700 3944 S 0.0 0.7 0:27.88 systemd
2 root 20 0 0 0 0 S 0.0 0.0 0:00.10 kthreadd
3 root 20 0 0 0 0 S 0.0 0.0 0:01.29 ksoftirqd/0
7 root rt 0 0 0 0 S 0.0 0.0 0:00.00 migration/0
8 root 20 0 0 0 0 S 0.0 0.0 0:00.00 rcu_bh
9 root 20 0 0 0 0 R 0.0 0.0 1:26.88 rcu_sched
10 root rt 0 0 0 0 S 0.0 0.0 0:03.87 watchdog/0
12 root 0 -20 0 0 0 S 0.0 0.0 0:00.00 khelper
13 root 20 0 0 0 0 S 0.0 0.0 0:00.00 kdevtmpfs
14 root 0 -20 0 0 0 S 0.0 0.0 0:00.00 netns
15 root 20 0 0 0 0 S 0.0 0.0 0:00.01 xenwatch
16 root 20 0 0 0 0 S 0.0 0.0 0:00.00 xenbus
18 root 20 0 0 0 0 S 0.0 0.0 0:00.14 khungtaskd
19 root 0 -20 0 0 0 S 0.0 0.0 0:00.00 writeback
20 root 0 -20 0 0 0 S 0.0 0.0 0:00.00 kintegrityd
21 root 0 -20 0 0 0 S 0.0 0.0 0:00.00 bioset
22 root 0 -20 0 0 0 S 0.0 0.0 0:00.00 kblockd
23 root 0 -20 0 0 0 S 0.0 0.0 0:00.00 md
28 root 20 0 0 0 0 S 0.0 0.0 0:00.24 kswapd0
29 root 25 5 0 0 0 S 0.0 0.0 0:00.00 ksmd
Below are the few description of the contents of TOP Command:
Job - Present time, how much time system is up, how many users connected, load average.
Task - How many total tasks, how many tasks running, how many tasks sleeping, how many tasks stopped, how many zombie process.
CPU - % of CPU used by users, % of CPU used by system, % of CPU used by nice value, idle CPU %, % of CPU wating for IO(to write), % of CPU used by Hardware Interupt, % of CPU used by Software Interupt, Steal time - used when there is a virtual box( delay in getting the actual CPU by virtual CPU in virtual systems)
Memory - Total RAM, Memory Used (Actually used - buffer), Memory Free( Actual + buffer + cache from swap) , Buffer( when system have free memory, it extracts few pages and keep it in buffer for caching, if system needs, it will give back the pages from buffer)
Swap- Total Swap, Swap Used, free, caching
PID - Process ID
USER - user through which process are running
PR - Priority - Process priority. 0 - highest priority 40 - Lowest
NI - Nice value - CPU Scheduling Priority. Utility through which we can set the priority manually. -19 -highest priority 20 - lowest priority
Virtual Memory - Each process cant access direct physical memory, so it uses virtual memory. Each process have its own virtual space. Physical memory address space is mapped to virtual memory address space. It is sort of security restriction where process cant directly indulge with Physical RAM. MMU - Memory Management Unit does the mapping between physical address space to virtual address space. pmap 1 shows mapping between VAS to PAS.
Resident Memory - Total Physical Memory that is non swapped.
Shared Memory - Memory that is being shared by other processes
S - state - Sleeping or running
% CPU - % of CPU used by the process
% MEM - % of Memory Used by the process
Time - How long is the process running
Command - What is the command that is being executed.
C - Process with obsolete path
k <pid> - to kill a process
z - Change color of top
r - for re nice a value
1 - shows the number of CPU
d - change refresh rate - Default 3 sec
A - Splits screen into multiple part/screen. Top Right Side says which split screen I am. So accordingly we can sort per split screen. Goto different split screen using a. Shift + a will toggle screen from small to big.
h - help
n - Reduce the number of listed process to n
I - To hide load average line
t - to hide CPU states. 2nd and 3rd line.
m - to hide/show the memory line. 4th and 5th.
top -u postgres or top and press u
top -n 2 stops refresh after 2 sec
top -p pid, pid
top -b -n 1
top -d3 -b -n 2 > top_output.txt.
top -H -p pid
Shift F - add extra column as required.
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