[Operating System] {ud923} P3L3: Inter-Process Communication

Visual Metaphor

Inter Process Communication

Message Based IPC

 Forms of Message Passing

 Shared Memory IPC

 Copy vs. Map

In windows:

(1), data size smaller than a threshold => copy

(2) othersiwe => copy to page aligned area and map

SysV Shared Memory 

Segments will be removed only when it‘s explicitly deleted or the system reboots

Whereas the regular non-shared memory that is malloced will disappear as soon as the process exists.

 SysV Shared Memory API

 https://www.tutorialspoint.com/inter_process_communication/inter_process_communication_system_v_posix.htm

 POSIX Shared Memory API

http://man7.org/linux/man-pages/man7/shm_overview.7.html

Shared Memory and Sync 

PThreads Sync for IPC 

Sync data be shared and visible to both processes.

 Here, system V api.

shmget(fork(segmentation_id, integer parameter), segment_size, area_permission)

　　segmentation_id => shared memory identifier => uniquely created from token operation => with arg[0] from command line

　　integer parameter => 120 here

　　segment_size => 1024 => 1KB

 　　return seg;

shmat(seg, ...)

　　return shared_memory_address;

IPC Resources

• SysV IPC Tutorials
  • has example source for SysV IPC
• mq_notify() man page
  • registers for notification when a message is available
• sem_wait() man page
  • locks a semaphore
• shm_overview man page
  • overview of POSIX shared memory

 Sync for Other IPC

 https://www.geeksforgeeks.org/ipc-using-message-queues/

IPC Command Line Tools

 Shared Mem Design Considerations

 How Many Segments?

 Design Considerations

[Operating System] {ud923} P3L3: Inter-Process Communication

原文：https://www.cnblogs.com/ecoflex/p/10920533.html