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tags: 作業系統
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# 作業系統 Ch3 Processes

### Process part
- text
- data section: global variable
- stack: temporary data
- heap

### PCB ( process control block )
- process state
- program counter
- CPU register
- CPU scheduling information
- momery management information
- accounting information
- I/O status information

### Scheduler
- long-term: determination degree of multiprogramming
- short-term
- I/O bound process
- CPU bound process

### multitask in mobile systems
- Android: background service use a service to platform tasks

### context switch
- time dependent on hardware support: sets of register per CPU -> multiple context load at once

### process termination
- cascading termination: if parent exit, child terminate
- zombie: if no parent waiting
- orphan: if parent terminate without invoking wait

### multiprocess architecture - Chrome
- browser
- renderer
- plug-in

### Interprocess communication
- cooperating advantage:
> information sharing
> computation speedup
> modularity
> convenience

- modal of IPC (interprocess communication)
> shared memory
> message passing

- Producer-Consumer problem
> unbounded-buffer: no limit buffer size
> bounded-buffer: fixed buffer size

- shared memory
> communication under user mode not os
> Major problem: synchronize
> POSIX

- message passing
> send、receive
> communication link
> example of IPC systems - Mach: msg based
> example of IPC systems - Windows: msg passing via LPC(local procedure call)、connection port、on the same system
>synchronize
>>blocking、Non-blocking
>>rendezvous: both send and receive is blocking

>buffering
>>zero capacity: no msg are queued on the link, sender must wait for receiver
>>bounded capacity
>>unbounded capacity

### Client-Server communication
- sockets:
>endpoint
>port 小於1024 well known
>3 socket type in Java: TCP、UDP、MulticastSocket)
- pipes
>ordinary pipes: undirectional
>names pipes: bidirectional、can access without parent-children relationship
- remote precedure calls
>stubs: client-side proxy for the actual procedure on server （Microsoft Interface Definition Language）
>marshall the parameter(從 memory 輸入到 hard disk 後傳送)
>msg pass exactly once
>external data representation (XDL) for different architecture
- remote method invocation (Java)

### command
- fork()
- exec(): replace the process memory space with program
- abort(): parent terminate execution of children process
- exit()
- grep(): search file content