Shulou(Shulou.com)05/31 Report--

This article mainly explains "how to check the usage of system resources under Linux". Interested friends may wish to take a look. The method introduced in this paper is simple, fast and practical. Let's let the editor take you to learn how to check the usage of system resources under Linux.

Information about CPU. When there is more than one CPU, these may be more than two lines. Eg.

Tasks: 115 total, 1 running, 114 sleeping, 0stopped, 0zombie

Cpu (s): 16.1% us, 2.0% sy, 0.0% ni, 79.5% id, 1.4% wa, 0.0% hi, 1.0% si

Tasks: 115 total number of total processes

1 running number of running processes

Number of sleeping sleep processes

0 stopped number of stopped processes

0 zombie number of zombie processes

Cpu (s): 16.1% us user space occupies CPU percentage

2.0% sy kernel space occupies CPU percentage

Percentage of CPU occupied by processes that have changed priorities in the process space of 0.0% ni users

79.5% id idle CPU%

1.4% percentage of CPU time wa waits for input and output

0.0% hi

0.0% si

The last two behaviors are memory information. Eg.

Mem: 8169876 k total, 7686472 k used, 483404 k free, 35272 k buffers

Swap: 4096532 k total, 160 k used, 4096372 k free, 2477532 k cached

Mem: 8169876 ktotal total physical memory

Total physical memory used by 7686472 k used

483404 k free total free memory

35272 k buffers memory used as kernel cache

Swap: total 4096532 k total switching partitions

Total number of switching areas used by 160k used

Total 4096372 k free free swap area

The total number of swap areas buffered by 2477532 k cached.

The contents of the memory are swapped out to the swap area, and then swapped into memory, but the used swap area has not been overwritten, and this value is the size of the swap area where these contents already exist in memory. When the corresponding memory is swapped out again, there is no need to write to the swap area.

Process information

The details of each process are displayed at the bottom of the statistics area. First of all, let's understand the meaning of each column.

PID USER PR NI VIRT RES SHR S CPU MEM TIME+ COMMAND

Serial number column name meaning

PID process id

PPID parent process id

RUSER Realusername

User id of the UID process owner

User name of the owner of the USER process

Group name of the owner of the GROUP process

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

PR priority

NInice value. Negative values indicate high priority, while positive values indicate low priority.

P the last use of CPU makes sense only in a multi-CPU environment

% percentage of time spent by CPU from last update to present CPU

Total CPU time used by TIME processes (in seconds)

Total CPU time used by the TIME+ process (in 100 seconds)

% percentage of physical memory used by the MEM process

The total amount of virtual memory used by the VIRT process, in kb. VIRT=SWAP+RES

The size of the virtual memory used by the SWAP process, in kb.

The amount of physical memory used by the RES process that has not been swapped, in kb. RES=CODE+DATA

The amount of physical memory occupied by CODE executable code, in kb

The amount of physical memory occupied by parts other than DATA executable code (data segment + stack), in kb

SHR shared memory size (in kb)

Number of nFLT page errors

The number of pages that nDRT has modified since it was last written.

S process status.

D = uninterruptible sleep state

R = run

S = sleep

T = track / stop

Z = zombie process

COMMAND command name / command line

WCHAN displays the name of the system function in sleep if the process is sleeping

Flags task flag, refer to sched.h

Sort by specified column

Top can be set to sort by a certain item. By default, it is sorted by CPU usage.

M, (note uppercase), sort by memory usage

P, sorted by percentage of CPU usage

T, sorted by time / cumulative time.

How to end the process

Enter the letter k (lowercase), and then enter the PID of the desired kill

Of course, you can also run the command directly, kill PID

As you can see, the top command is a very powerful tool for monitoring the system, especially for system administrators. However, its disadvantage is that it consumes a lot of system resources.

II. Free command

1. Action

The free command is used to show memory usage, with permissions for all users.

two。 Format

Free [- b-k-m] [- o] [- s delay] [- t] [- V]

3. Main parameters

-b-k-m: displays memory usage in bytes (KB, MB), respectively.

-s delay: displays the number of seconds per second to show memory usage.

-t: displays the memory sum column.

-o: the buffer adjustment column is not displayed.

4. Application example

The free command is the main command used to view memory usage. Compared with the top command, it has the advantage of being easy to use and consuming only a small amount of system resources. With the-S parameter, you can use the free command to continuously monitor how much memory is used, so that it can be used as a convenient real-time monitor.

# free-b-S5

After using this command, the terminal will continuously report memory usage (in bytes), updated every 5 seconds.

3. Uptime command

In the linux system, there is a saying that when load avarage

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