9-17 Linux process View and management

Linux process viewing and management

Basic features of the OS: file system, network functions, process management, memory management, drivers, security features

program = instruction + data

Cpu:
Privileged Directives
General Instructions

Program execution Environment:
Kernel mode: Run kernel-level directives
User mode: Run General Instructions

Application:
Run normal command: Run directly on the CPU
Run privileged command: via system call

Memory: 8bits, 1byte
32bits, 2^32, 0-2^32-1, 2^10*2^10*2^10*2^2 bytes = 2^10*2^10*2^2 Kilo bytes = 2^10*2^2 MB = 4GB
64bits, 2^64, 4billions 4G

4G:1G, kernel
3G, App

Rom+ram
ROM, RAM

Address space:
Physical Address space
Linear address space

Ipc:inter Process Communication
Same host:
Signal
Semerphor
SHM (Shared memory)

Different hosts:
Rpc:remote Procedure Call
Socket

Process scheduling:

Multitasking: Multi-process running at the same time
Preemptive multi-tasking

Process classification:
CPU Bound:cpu Intensive
I/O Bound:io intensive

Process priority:
140:0-139
1-99: Real-time priority, the higher the number, the greater the priority
100-139: The smaller the number, the higher the priority;
Static priority
Dynamic priority

Algorithm time complexity: Big O
O (1)
O (LOGN)
O (N)
O (n^2)
O (2^n)

Process creation:
Request Issuer: Process
Process: Fork (), Clone ()

Cow:copy on Writing
Copy when writing

Status of the process:
Operating state: Running
Sleep state: Sleeping
Interrupted sleep: interruptible
Non-disruptive sleep: uninterruptible
Processes that are blocked by IO
Ready state: Runnable
Stop state: Stopped, can not be scheduled to run state;
Zombie State: Zombie

Process Management:
Task struct: Used to hold each process meta-data information
Example: PID, Ppid, memory, thread, files

Task List: Saves the task struct for each process with a data structure called a "linked list"

Process switching: Context switch
Save site:
Recovery site:

OS: The provision of virtual computers, which enables the use of limited resources through the "protection" mechanism to allocate multiple simultaneous programs, that is, "process" to achieve the so-called multi-tasking;

Process:
Thread: Tread
Share the resources of the process, such as open files, etc.;
A lighter-weight, individually-scheduled operating unit;

Lwp:light Weight Process

Linux process viewing and management tools: Top, Pstree, PS, Pidof, Pgrep, Pkill, Htop, Glances, Pmap, Vmstat, Dstat, Iostat, SAR, kill, Job, BG, FG

All child processes except Init on Linux systems are made up of their parent process fork (), followed by the cow mechanism, and the process is presented as a "process tree";

Pstree command:
Process tree view;
-P: Shows the PID of each process;

Ps:process State

The information about kernel in Linux running is output by/proc pseudo file system; Each process has a subdirectory named after its PID, and many files in each subdirectory store the related state information of the process;

The display is a snapshot of the current process state information on the system when the PS command executes, so, for static results;

Many options are supported:
BSD Style
SYSV style

Depending on whether the process started interactively from the user interface on the terminal, the process can be divided into two categories:
Terminal-related processes: a
Terminal-independent processes: X

User-centric organization of process status information display: U

Common option Combination 1:axu
USER PID%cpu%MEM VSZ RSS TTY STAT START time COMMAND

Vsz:virtual Memory Size
The amount of space occupied by the linear address space;
RSS: Commonly used in memory sets, refers to the amount of data that can not be exchanged to swap space to occupy space;

STAT: Process Status
R:running, running state;
S:interruptible sleeping, can interrupt sleep
D:uniterruptible sleeping, non-disruptive sleep
t:stopped
Z:zombie

S:session leader
+: Foreground process, occupy a terminal
L: Multithreaded Process
<: high-priority process
N: Low-priority process

Start: Startup time
Time: Occupy CPU cumulative duration
Command: Starts the shell of the current process or thread, [] represents a kernel thread;

Common option Combination 2:-ef
-e: Show All Processes;
-F: Display rich formatting information

Common option Combination 3:-EFH
-F: Show additional information
-H: Show the inter-process relationship in a hierarchical form;

Customizing the information you need to display: Axo
PS Axo Pid,command,psr,pri,ni
PSR: The CPU number of the current process running;
PRI: Priority of the current process;
NI: The nice value of the current process;
-20, 19

Pgrep:
Syntax format: pgrep [OPTIONS] "PATTERN"
-U UID: Displays only the processes running as the specified user;
-G GID
-L: Show PID and process name;

Pidof:
PIDOF Program
Program: Given a command-line procedure

Top command:
There are many interactive sub-commands;
P: Sort by the percentage of CPU occupied;
M: In order to occupy memory space size;
T:CPU cumulative occupancy time sequencing;

L: Whether the system load line is displayed;
Reasonable interval of queue Length: number of CPUs *0.7
T: whether to display the process summary information and CPU load status;
Cpu (s): 0.0%us, 0.0%sy, 0.0%ni,100.0%id, 0.0%wa, 0.0%hi, 0.0%si, 0.0%st
Us:user Space
Sy:system (kernel space)
Ni:nice
Id:idle
Wa:wait IO
Hi:hardware Interrupt
Si:software Interrupt
St:stolen, percentage of "stolen" by virtual machine
1: Average or separate display of CPU load status;
M: Whether to display memory-related status information;

Q: Exit command
S: Modify the delay length
K: Terminates the specified process

Options for the top command:
-b:batch, Batch Display
-N #: Number of batches displayed
-D #: Indicates how long the delay is

Uptime command: Displays the current system time, the running time, the number of users logged in and the average system load;

Command summary: Pstree, PS, Pgrep, top, uptime, pidof


Review:
Process Management
Task struct: Meta-data information for each process, such as the pid,ppid of the process, thread, files
Task List: Lists of tasks, linked tables

Linear address space for the process:
Text Segment
Data Segment
BSS Segment
Heap
Stack

Process Status:
Ready state, operating state, sleep (interruptible, non-interruptible), stop state, zombie state

Process priority:
Real-time priority
Static priority:
100-139
Dynamic priority

Process View Basic tools: Pstree, PS, top, pidof, pgrep, uptime
Ps:axu,-ef,-EFH, Axo
Top:p,m,t,l,t,m,s,q,k

Linux process View and management (2)

Htop
Interactive commands:
U: Filter only shows the process of the selected user;
S: Tracks the system calls initiated by the selected process;
L: Displays the files opened by the selected process;
T: Displays the hierarchy of processes;
A: Sets the CPU affinity of the process; (binds the selected process to the specified CPU)

Options:
-D #: Delay duration
-U USERNAME: Displays only the process of the specified user;
-S COLUMN: Sorts according to the specified field;

Vmstat command:

Usage: vmsate [delay [count]]

Procs:
R: The number of processes waiting to run; (Queue Length)
B: The number of processes that handle the non-disruptive sleep state (that is, IO blocking queue Length)

Memory
SWPD: Swap memory usage;
Free: The amount of physical memory in space;
Buffer: The total amount of memory used for buffer;
Cache: The total amount of memory used for the cache;

Swap
Si: The rate at which data enters the swap (KB/S)
So: the rate at which data leaves swap (kb/s)

Io
BI: The rate at which data is read from the block device to the system (KB/S)
Bo: The rate at which data is saved to a block device (KB/S)

System
In: Interrupt rate
CS: Rate of process switching

Cpu
us
Sy:
Id:
Wa
St:

Options:
-S: Displays status statistics for memory

/proc/#接口:

Pmap: View the memory mapping relationship of the specified process;
Pmap [OPTIONS] pid ...
-X: Show Extended information

Cat/proc/#/maps

Glances:
glances [-BDEHMNRSVYZ1] [-B bind] [-C Server] [-C conffile] [-P port] [-p password] [--password] [-t refresh] [-f file] [- O Output]

Common options:
-B: Display the data exchange rate of the network card device in BYTE/S;
-D: Turn off the disk I/O function module;
-f/path/to/somefile: Set the location and format of the output file;
-O {html| CSV}:
-M: Turn off the Mount function module
-N: Turn off network function module
-r: Close Process List Function module
-T #: Specifies the length of the delay, which defaults to 3 seconds;
-1: Display each CPU related load data information separately;

Glances supports remote mode:
That can work in C/s mode:
Server: Start glances in listening mode;
Client: Start glances in remote mode, connect to the specified server remotely, and correlate data on server;

Service mode:
Glances-s-B ipaddr
-B: Used to indicate the local address of the listener;

Client mode:
Glances-c ipaddr
-C: The address of the server used for the connection;

Dstat: Integrates the functions of the Vmstat, Iostat, Netstat and ifstat four tools;
Dstat [-AFV] [options:] [Delay [Count]]

-C: Displays statistical data related to CPU performance indicators;
-D: Show disk-related rate data;
-G: Displays page-related rate data;
-I: Show interrupt related rate data;
-L: Displays statistics related to load average;
-M: Display memory related statistics;
-N: Shows the rate of data sent and received by the network;
-P: Displays process-related statistics,
The rate of-r:io requests;
-S: Show data about swap
-Y: Displays system-related data, including interrupts and process switching;

--TOP-CPU: Displays the most CPU-intensive processes;
--top-bio: Shows the process that consumes block IO most;
--top-io: The most IO-intensive process;
--top-mem: Shows the most memory-intensive processes;

--IPC: Shows the rate data related to interprocess communication;
--raw: Displays data related to raw sockets;
--TCP: Displays data related to TCP sockets;
--UDP: Displays data related to UDP sockets;
--unix: Displays statistics related to UNIX sock interfaces;
--socket:

-A:-cdngy

IPC: Inter-process communication
Common forms:
Message Queue
Semerphore
Shared memory
Signal

Signal: Short information passed to a process
Information that is available between processes supported by Linux hosts:
(1) kill-l
(2) Man 7 signal

Signal to process:
Kill [-signal] PID
The default signal is sigterm;

Signal representation:
(1) Full name, e.g. SIGINT
(2) abbreviated name, e.g. int
(3) Data McCartney, e.g. 2
Common signals:
Sighup:1, notifies the process to reread its configuration file for the new configuration to take effect without restarting the process;
Sigint:2, interrupting a running process, equivalent to a keyboard key combination CTRL + C
Sigkill:9, forcibly aborting a running process
Sigterm:15, safely aborting a running process
Sigstop:19, pausing the process
SIGCONT:18, continue running the specified process

Kill a similar set of processes:
Killall [-signal] Program

Command summary: Htop, Vmstat, glances, Dstat, kill, Killall

Job Management:
Front-end operation: Start through the terminal, and will occupy the terminal until it stops;
Background job: When the job starts, it is not related to the terminal, or it is started in the foreground, but it is switched to terminal-independent mode.

How do I get my job running in the background?
1. For jobs that are already up and running:
CTRL + Z

Note: When the job is sent backstage, the default is in stopped state;
2. For jobs that have not been started:
COMMAND &

Note: This two-way related job is still related to the terminal, which means that termination of the terminal will cause all jobs associated with this terminal to be terminated;

The relationship between the stripping process and the terminal:
# Nohup COMMAND &

Job View:

Jobs command
Job number, job status, Startup command-line program

Job Control Commands:
FG [[%]job_num]: The assigned assignment is recalled to the foreground;
BG [[%]job_num]: The designated job in the background to start up, let its background silently run, but this job must support running in the background;
Kill [%job_num]: terminates the specified job;

Process Priority tuning:
Static priority:
The priority is adjusted by specifying the nice value of the process, and the process of user space running generally has its nice value;
Nice value:-20, 19
Priority: 100, 139

When the process is started by default, its nice value is 0 and its priority is 120;

(1) For processes that have not yet started:
# nice-n N COMMAND

(2) for a process that is already up and running:
# renice-n N PID

Note: Ordinary users can only adjust the size of nice, lower priority;

Orders not yet spoken: SAR, Iostat, Ifstat, tsar;

Command summary: Jobs, FG, BG, Nice, Renice

Blog job: The use of process management tools htop/glances/dstat;

9-17 Linux process View and management