How to use the Monitor command top command in Linux

Collected two articles about how to use the Monitor command top command in Linux for more information. In general, the top command is mainly used to view the Linux system's various processes and system resource consumption, in monitoring the performance of Linux system top is very useful, the following is my collection of the Linux top command article, I hope to help everyone

Top as one of the most common and important Linux system monitoring tools in daily management work, can observe the status of system process dynamically. The top command displays a number of items, with the default value being updated every 5 seconds and pressing the Q key to exit. The items shown are:-B: Batch mode run. -C: Displays the command line that performs the task. -D: Sets the delay time. -H: Help. -H: Displays the thread. The threads generated by all processes are displayed. -I: Shows the idle process. -N: Number of executions. Typically used with-B. -U: monitors the specified user-related processes. -U: monitors the specified user-related processes. -P: monitors the specified process. -S: Safe mode operation. -S: Cumulative time mode. -V: Displays the top version and then exits. -M: Automatic display of memory units (k/m/g).

Uptime This item shows the system boot time, elapsed time, and three average load values (last 1 seconds, 5 seconds, 15 seconds of load value).

Processes the total number of running processes since the most recent refresh. These processes are divided into running, dormant, and stopped.

CPU states shows the percentage of CPU time consumed by user mode, System mode, priority process (only the priority is negative) and idle, etc. The time consumed by the priority process is also included in the user and system time, and the total percentage will be greater than 100%.

Mem memory usage statistics, which includes total available memory, free memory, memory used, shared memory, and memory occupied by the cache.

Swap swap space statistics, which includes total swap space, usable swap space, and swap space.

PID Id,ppid Each process's parent process ID for each process. UID per process owner, user name per process owner, PRI per process priority, NI priority value for the process. Size the number of the process's code, plus the size of the data, plus the total amount of stack space, in kb.tsize the process's code size. This is a very strange value for kernel processes. Dsize the size of the data and stack. TRS text resident size. D is marked as "dirty" page item. The size of the library page that LIB uses. does not work for elf processes. RES the total amount of physical memory that the process occupies, in kilobytes. SHARE The amount of shared memory that the process uses. STAT the status of the process. s= Hibernate, d= dormant, r= run, z= Zombie, t= stop or trace. Time the total CPU time that the process has occupied since it was started, and if it is in the cumulative mode, the time will also include the duration of the process's child process. And the title will become CTime. %cpu the percentage of CPU time and total time that the process has occupied since the most recent refresh. %mem the percentage of total memory that the process occupies in physical memory. command name of the process, and if one line does not appear, it will be intercepted. The in-memory process will have a complete command line.

From: http://www.linux521.com/2009/system/201201/17945.html

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What does the CPU information in the top command of Linux mean?
Cpu (s): 62.1% us, 15.9% sy,0.1% ni, 19.4% id,2.0% wa,0.1% hi,0.4% si
mem:8247956k total,8232004k used,15952k free,205240k buffers
swap:8191992k total,48k used,8191944k free,7156092k Cached
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.
top–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% us, 1.0% sy, 0.0% ni, 98.7% ID, 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
Statistical information Area
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.
Change what is displayed
The F key allows you to select what is displayed. Press the F key to display a list of columns, press A-Z to show or hide the corresponding column, and then press ENTER to confirm.
Press the O key to change the order in which the columns are displayed. A-Z in the lower case moves the corresponding column to the right, while the uppercase A-Z moves the corresponding column to the left. Finally, press ENTER to confirm.
Press the uppercase F or O key, and then press A-Z to sort the process by the appropriate column. The uppercase R key can reverse the current sort.
command to use
1. Tool (command) name
Top
2. Tool (command) function
Displays the current process and other status of the system; Top is a dynamic display process that allows you to continuously refresh the current state by pressing the user key. If the command is executed in the foreground, it will monopolize the foreground until the user terminates the program. More accurately, the top command provides real-time status monitoring of the system's processor. It will display the most "sensitive" task list on the system. This command can be used by CPU. Memory usage and execution time sorting tasks , and many of the features of the command can be set through interactive commands or in personal customization files.
3. Environment settings
Used under Linux.
4. How to use
4. 1 Using formats
Top [-] [d] [P] [Q] [C] [s] [s] [n]
4. 2 parameter description
d Specifies the interval between every two times the screen information is refreshed. Of course the user can use the s interactive command to change it.
P only monitors the state of a process by specifying the monitoring process ID.
Q This option will cause top to refresh without any delay. If the calling program has Superuser privileges, top will run at the highest possible priority.
S Specifies the cumulative mode
s enables the top command to run in Safe mode. This removes the potential danger of interactive commands.
I make top not show any idle or zombie processes.
C Displays the entire command line instead of just displaying the command name
4.3 Other
The following are some of the interactive commands that you can use during the execution of the top command. From a point of view of use, mastering these commands is more important than mastering the options. These commands are single-letter, and if you use the S option in command-line options, some of these commands may be masked out.
Ctrl+l Erase and rewrite the screen.
H or? Display the help screen and give a brief summary of the commands.
K Terminates a process. The user will be prompted for the process PID to be terminated and what signal needs to be sent to the process. The normal termination process can use a 15 signal, and if not, use signal 9 to force end the process. The default value is signal 15. This command is masked in safe mode.
I ignore idle and zombie processes. This is a switch-type command.
Q quit the program.
R reschedule the priority level of a process. The user is prompted to enter the process PID that needs to be changed and the process priority value that needs to be set. Entering a positive value lowers the priority and, conversely, it gives the process a higher priority. The default value is 10.
S switch to cumulative mode.
s changes the delay time between two refreshes. The user will be prompted to enter a new time in S. If there are decimals, it is converted into M S. Enter a value of 0 and the system will refresh continuously, the default value is 5 S. It is important to note that if you set too small a time, it is likely to cause a constant refresh, so it is too late to see the display, and the system load will be greatly increased.
F or F Add or remove items from the current display.
O or O change the order in which items are displayed.
L Toggle Display Average load and start time information.
M toggles display memory information.
T toggles the display of process and CPU status information.
The C toggle Displays the command name and the full command line.
M sorts based on the size of the resident memory.
P is sorted according to the percentage size of CPU usage.
T is sorted by time/accumulated time.
W writes the current settings to the ~/.TOPRC file. This is the recommended way to write top configuration files.

How to use the Monitor command top command in Linux