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
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
