Detailed explanation of linux top command

Press 1 to see the usage of each CPU

first row

Current time Running time Current logged in user Load balancing (1 minute, 5 minutes, 10 minutes)

Load average data checks the number of active processes every 5 seconds and calculates the value. If the number divided by the number of logical CPUs exceeds 5, the system is overloaded.

second line

Total 248 processes 1 running 247 sleeping 0 stopped 0 zombie processes

The third row

us (user space): The percentage of CPU occupied by user space

sy (sysctl): The percentage of CPU occupied by kernel space

ni()—Percentage of CPU occupied by processes that have changed priority

id(idolt): Idle CPU percentage

wa(wait): IO waiting percentage of CPU occupied

hi (Hardware IRQ): Percentage of CPU occupied by hard interrupts

si (Software Interrupts): The percentage of CPU occupied by soft interrupts

Fourth line

Total memory Used memory Free memory Buffers (amount of cached memory)

The fifth line

Swap partition

Available memory=free buffer cached (total amount of swap area in Huancheng)

For memory monitoring, in top we must always monitor the used of the swap partition in the fifth line. If this value is constantly changing, it means that the kernel is constantly exchanging data between memory and swap. This is a real lack of memory. .

The total amount of memory in use (used) in the fourth line refers to the amount of memory currently controlled by the system kernel,

The total amount of free memory (free) in the fourth line is the amount that the kernel has not yet included in its control.

Not all the memory managed by the kernel is in use, it also includes memory that has been used in the past and can now be reused. The kernel does not return these reusable memories to free, so on Linux Free memory will become less and less, but don't worry about this.

Sixth line

PID — process id

USER — Process owner

PR — Process Priority

NI — nice value. Negative values ​​represent high priority, positive values ​​represent low priority

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

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

SHR — Shared memory size, unit kb

S —Process status. D=Uninterruptible sleep state R=Run S=Sleep T=Trace/Stop Z=Zombie process

%CPU — The percentage of CPU time occupied since the last update

%MEM — Percentage of physical memory used by the process

TIME — Total CPU time used by the process, unit 1/100 second

COMMAND — Process name (command name/command line)

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