Presented the first plurality of programs can be simultaneously calculated in a computer
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1. encountered IO let the cpu
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2. cpu give other programs so that other programs can use cpu
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3.cpu let the matter take up time
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4. The two program switching back and forth on a cpu, not mess
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Each program has a separate memory space
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Each program record in the current state before and after the switching will
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calculating and computing cpu not (IO) operations
IO operation is not accounted for cpu
IO operation (operation network file operations): input and output (relative memory)
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Obstruction: sleep / input / recv / accept / recvfrom / cpu is not required to participate in
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The read file: the first reading operation of the disk opposite to the bar codes 90w
input: data (from disk) to the memory input
read/load/input/recv/recvfrom/accept/connect/close
output: output data from memory
write/dump/print/send/sendto/accept/connect/close
IO operations are essentially all file operations
input/print
input is written to the file, and the contents of the input file is loaded into memory by reading the
print is written directly to a file, and then look through the documents presented to the user
Interactive method of socket: all file operations
send a file is written to the cache
recv is read from the cache file
That is at least as far as the operation of the IO is a cpu is the execution time of 0.009s = 90w bar code python
cpu calculated only read into the data memory, the other is not read into memory is not calculated
Round-robin algorithm - sharing operating system
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1. The time slice to just let the cpu
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2.cpu let out it takes time
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3. reduced efficiency, to provide user experience
Mononuclear 1cpu can only run one program
The concept of process
Procedures and processes (minimal computer resource allocation units)
Running program is the process
Data between a process and the process is isolated
Thread (the smallest unit of a computer operating system that can be scheduled)
Each location to which the program execution is recorded
There is one thread in the process responsible for the implementation of specific programs
Process is managed by the operating system
Scheduling process (operating system complete):
Scheduled by the operating system, each process has at least one thread
Short operating priority algorithm
First come first serve algorithm
Round-robin algorithm
Multilevel feedback algorithm
Start the process of destruction
Start the process: 1 interaction (double-click) 2. Start another 3 at startup in a process
The program is responsible for starting a process is called a parent process
The process started is a child process
Destruction: the interaction is killed by another process (at the end of the parent process child process) wrong end of the process
Parent and child
The parent process child process open
The parent process will also be responsible for the end of child processes for resource recovery
The process of the above mentioned id processid pid
On the same machine the same time there can be no duplicate process id
The process id can not set the operating system is randomly assigned
With the process id multiple runs a program may be assigned multiple times each time is different
Three-state map process
Ready ready to run run blocking block
import os
import time
print(os.getpid())
print(os.getppid()) # parent process id
time.sleep(100)
Module mutilprocessing Module: Built-in module
multiple diversification
processing process
Import os
Import Time
from multiprocessing Import Process
DEF FUNC (): "" " FUNC executed in the process : return: " "" Print ( 'child process:', os. getpid (), os. getppid ()) Time. SLEEP ( . 3) IF the __name__ == 'main': P = process ( target = FUNC) P. Start () Print ( 'primary process:', . OS getpid ()) to the child process parameter passing DEF foo ( A): "" " foo executed in the process : return: """
print('子进程：', a)
time.sleep(3)
if __name__ == '__main__':
p = Process(target=func, args=(1,))
p.start()
Parallel: a plurality of programs are simultaneously performed cpu
Concurrent: run multiple programs at the same time looks
Synchronous: A program execution over again to call another and have to wait for the program is finished in the procedure call
Asynchronous: A program execution over the call to another but do not wait for the completion of this task will continue
Blocking: cpu does not work