Linux Command TOP

Top Command

The top command is a common performance analysis tool under Linux that shows the resource usage of individual processes in the system in real time, similar to the Task Manager for Windows. Here is a detailed description of how it is used.

The top display results are as follows:

01:06:48 up 1:22, 1 user, load average:0.06, 0.60, 0.48

tasks:29 Total, 1 running, sleeping, 0 stopped, 0 zombie

Cpu (s): 0.3% user, 1.0% system, 0.0% Nice, 98.7% idle, 0.0% wa, 0.0% Hi, 0.0% si

mem:191272k Total, 173656k used, 17616k free, 22052k buffers

swap:192772k Total, 0k used, 192772k free, 123988k cached

PID USER PR NI VIRT RES SHR S%cpu%MEM time+ COMMAND

1379 Root 0 7976 2456 1980 S 0.7 1.3 0:11.03 sshd

14704 Root 0 2128 980 796 R 0.7 0.5 0:02.72 Top

1 Root 0 1992 632 544 S 0.0 0.3 0:00.90 Init

2 Root 0 0 0 S 0.0 0.0 0:00.00 ksoftirqd/0

3 root RT 0 0 0 0 S 0.0 0.0 0:00.00 watchdog/0

The first five elements are the statistical information of the whole system.

The first line is the task queue information, with the execution result of the uptime command. The contents are as follows:

01:06:48 Current Time

Up 1:22 system run time, format last: minutes

1 user Current number of users logged on

Load average:0.06, 0.60, 0.48 system load, which is the average length of the task queue.

The three values were 1 minutes, 5 minutes, and 15 minutes ago to the present average.

The second to third behavior process and CPU information. When there are multiple CPUs, the content may be more than two lines. The contents are as follows:

tasks:29 Total Process Totals

1 running number of running processes

Sleeping the number of sleep processes

0 Number of processes stopped stopped

0 Zombie Number of zombie processes

CPU (s): 0.3% US user space consumes CPU percentage

1.0% SY core space CPU percent occupied

0.0% CPU Percentage of processes that have changed priority within NI user process space

98.7% ID Idle CPU percent

0.0% wa wait for the input output CPU time percentage

0.0% hi

0.0% si

The last two behavior memory information. The contents are as follows:

MEM:191272K Total Physical Memory

Total physical memory used by 173656k used

17616k free Memory Total

The amount of memory that 22052k buffers uses as the kernel cache

Total swap area of swap:192772k

Total swap area used by 0k used

192772k Free Swap Area total

123988k cached Buffers The total number of swap areas.

The in-memory content is swapped out to the swap area and then swapped in to memory, but the used swap area has not been overwritten.

This value is the size of the swap area where the content already exists in memory.

When the corresponding memory is swapped out again, it is no longer necessary to write to the swap area.

Process Information Area

The details of each process are shown below the statistics area. Let's start by understanding the meaning of the columns.

Ordinal column name meaning

A PID process ID

b PPID Parent Process ID

C ruser Real User name

D UID Process Owner's user ID

e username of user process Owner

Group name of the F group Process owner

The terminal name of the G TTY boot process. Processes that are not started from the terminal are displayed as?

H PR-Priority

I NI nice value. Negative values indicate high priority, positive values indicate low priority

The last CPU used by J P is meaningful only in a multi-CPU environment

K%cpu CPU time consumption percentage last updated to current

The total CPU time, in seconds, used by the timing process

The total CPU time used by the M time+ process, in units 1/100 seconds

n the percentage of physical memory used by the%MEM process

o The total amount of virtual memory used by the VIRT process, in kilobytes. Virt=swap+res

The P swap process uses the size of the virtual memory, which is swapped out, in kilobytes.

The size of the physical memory, in kilobytes, that the Q RES process uses and has not been swapped out. Res=code+data

R code executable code occupies the physical memory size, in kilobytes

The amount of physical memory that is used outside of the S data executable code (data segment + stack), in kilobytes

T SHR shared memory size, in kilobytes

U Nflt page Error count

V NDRT the number of pages that have been modified in the last write to now.

W S Process state.

d= non-disruptive sleep state

R= Run

S= Sleep

t= Tracking/Stopping

z= Zombie Process

x command name/command line

Y Wchan If the process is sleeping, the system function name in sleep is displayed

Z Flags task Flag, reference sched.h

By default, only the more important PID, USER, PR, NI, VIRT, RES, SHR, S,%cpu,%MEM, time+, and command columns are displayed. You can change the display by using the following shortcut keys.

Linux Command TOP