Linux operating system-command-top

Concept

Top,display Linux tasks, that is: Show Linux processes/tasks.

A usage within Linux

Top

This command means: "Resource usage per process" is displayed. In our performance testing process, we often need to use this command to view the load status of the server.

An introduction to the fields in the output list line 1th

Line 1th		Note
16:33:23	Current time
Up 5:58	The system has been running for 5 hours and 58 minutes.	If the machine is running for more than 24 hours, Then "N Days" will appear on the left.
4 Users	Number of currently logged on users
Load Average	System load	The three values are: 1 minutes, 5 minutes, 15 minutes ago to the current average of system load

Line 2nd

Line 2nd –tasks		Note
Total	Total number of processes 150
1 Running	Running Processes 1
149 Sleeping	Process of sleep 159
0 stopped	The process of stopping
0 Zombie	Zombie Process

Line 3rd

Line 3rd –cpu (s)		Note
0.2%us	User space consumption CPU percentage (user usage)
0.2%sy	CPU Percentage of kernel space (System usage)	If it is too high, it indicates a long system call, such as frequent IO operations
0.0%ni	CPU percentage of processes that have changed priority in user process space
99.6%id	Percentage of idle CPU
0.0%wa	Percentage of CPU time waiting for input and output
0.0%hi	Hard Interrupt	IO Interrupt
0.0%si	Soft interrupt	Network outage
0.0%st	Percentage of time that the virtual CPU waits for the actual CPU	Full Name: Steal time A high steal value may mean that the host vendor sells the virtual machine over the server over and over again. If you upgrade a virtual machine and the steal value is not down, you should look for another service provider. A low steal value means that your application works well on the current virtual machine. Your virtual machine responds faster because your virtual machines don't often compete fiercely with other virtual machines for CPU time. This also implies that your hosting provider does not sell virtual services over an excessive amount, which is definitely a good thing.

Line 4th

Line 4th –mem		Note
2061556 k Total	Total Physical Memory
1626384 K Used	Total amount of physical memory used
435172 k Free	Amount of free memory
56504 K Buffers	Amount of memory used as the kernel buffer	"Buffer" is called "buffering" "Buffer is the data that is about to be written to disk, and the data is stored intact."

Line 5th

Line 5th –swap		Note
0k Total	Total Swap Area
0k used	Total number of swap areas used
0k Free	Total Free Swap Area
173428k Cached	Total number of swap areas cached	"Cache" is called "Caching" "The cache is the data being read from the disk and waiting to be used."

The so-called 6th line

Line 6th – Process information		Note
Pid	Process ID	PPID: Parent Process ID
USER	User name of the process owner	UID: User ID of the process owner
PR	Priority level
NI	Nice value	A negative value indicates a high priority, Positive values indicate low priority
VIRT	Total amount of virtual memory used by the process, in kilobytes	Virt=swap+res
Res	The amount of physical memory that the process uses, not swapped out, in kilobytes	Res=code+data
Shr	Shared memory size, in kilobytes
S	Process status	d= non-disruptive sleep state R= Run S= Sleep t= Tracking/Stopping z= Zombie Process
%cpu	CPU time consumption percentage last updated to current
%MEM	Percentage of physical memory used by the process
time+	Total CPU time used by the process, Unit 1/100 sec
COMMAND	Command name/command line

Linux operating system-command-top