Linux Learning Notes < 16 >--Process Management

Process/thread Model

Stopped: The process stops running after it receives a stop signal

Ready: Running

Executing is waiting in the running queue

Uninterruptible sleep: Non-terminal refers to the CPU does not respond to external hardware interrupts, but the process does not respond to asynchronous signals

Interruptible sleep: Waits for certain events to occur and is suspended

Zombie: The process has been terminated, but the process control blocks (and a few resources) of the processes have not been recycled

Program Priority , the smaller the number, the higher the priority, the more priority to get the opportunity to run, get more CPU run time

0-99: Kernel control

100-139: Users can control

Nice value : Elegant, friendly, smaller, more preferred

Ordinary users can only change the nice value of the large process, cannot be changed to small

process number : 1-65535

Init's process number is always 1, which is the parent process for all processes

Ps:process State

Style:

System v Style: option to use-

BSD style: Option not required-

A: Show all processes associated with the terminal

U: Show more detailed information

x: All processes unrelated to the terminal

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Ps-o Pid,ni, the foreground only process is displayed by default, Ps-axo Pid,ni Show All Processes

Process status in PS query:

D: Non-terminal sleep

R: Run or ready

S: interruptible Sleep

T: Stop

Z: Zombies

<: high-priority process

N: Low-priority inheritance

+: Processes in the foreground process group

L: Multi-threaded inheritance

S: The first process of the session process

The command field in the PS query is represented by a thread in the kernel.

pgrep: Show process PID under specific conditions

Pgrep [OPTIONS] CONDITION

-L: Simultaneous display of process and PID

-O: When matching multiple processes simultaneously, the one with the smallest process number is displayed

-N: The one that displays the largest number of processes when matching multiple processes simultaneously

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pidof: Show PID for a specific process

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Top: Real-time monitoring of process information, by default based on the percentage of cups from large to small sort

-D #: Specifies the amount of time to refresh, in seconds

-B: Batch mode, displaying information for all processes

-N #: Number of refreshes in batch mode

Interactive commands for top:

M: Sort based on the size of the resident memory

P: Sort by CPU percent usage

T: Sort by cumulative time

L: Show average load and start time

T: whether to display process and CPU status related information

M: whether memory-related information is displayed

C: Whether to display full command line information

Q: Exit Top

K: Terminate a process

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kill: Send a signal to the process

Kill [OPTION] PID

Important signals in Kill:

1:sighup allows a process to reread a configuration file without restarting it and let the new configuration information take effect

2:sigint Ctrl + C interrupts a process

9:sigkill kills a process and forcibly kills

15:sigterm terminates a process, terminates at the correct process, and the default option

Specify a signal:

Signal Number: KILL-1

Signal Name: Kill-sigkill

Signal name shorthand: Kill-kill

Note: Kill can only receive PID and%jobid,killall only the process name

To adjust the nice value :

To adjust the nice value of a process that has already started:

Renice NI PID

Specify a nice value at startup:

Nice-n NI COMMAND

Front desk and backstage

Foreground job: Occupy command prompt

Background job: After startup, release the command prompt, and subsequent operations are completed in the background

Front desk--Backstage:

CTRL + Z: Send the job at the front desk to the backstage

Command &: Let commands execute in the background

Jobs: View all jobs in the background

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BG: Let the stop job in the background continue to run

[JOBID]: The default does not add job number to perform a job with +

FG: Back-office jobs to the foreground

[[%]jobid]: The default does not add job number to perform a job with +

Kill%jobid: Terminate a job

vmstat: displaying virtual memory information

# *: Every # seconds refresh, refresh * times

Linux Learning Notes < 16 >--Process Management