Intro To Os P3L3: Inter-Process Communication

Front 1

What is Inter-Process Communication?

Back 1

OS-supported mechanisms for interaction among processes (coordination & communication)

Front 2

What are some types of IPC?

Back 2

1. Message based - Passing messages across sockets, pipes, etc.

2. Memroy based - Shared memory, memory mapped files, etc.

Front 3

Describe message-based IPC

Back 3

1. Supports sending and receiving of messages

2. OS creates and maintains a channel (buffer, FIFO queue, etc).

3. OS provides an interface to the processes - a port

4. Processes read/write to/from port

5. Kernel performs each IPC operation and establishes communication channel

Front 4

What are advantages and disadvantages to Message-based IPC?

Back 4

Advantages

1. Simplicity: Kernel manages channel and message passing

Disadvantages

1. Overheads due to system calls

Front 5

What are some methods of Message-Passing IPCS?

Back 5

1. Pipes - Carry byte stream between two processes. Output of one process can be input to another process.

2. Message Queues - Carry messages "among" processes.

3. Sockets - Send/Recv messages through kernel communication buffers

Front 6

Describe Shared-Memory IPC

Back 6

Processes read and write into a shared region. This region is mapped into the virtual address space of both processes, and points to the same area of physical memory.

Front 7

What are advantages and disadvantages to Shared-Memory IPC?

Back 7

Advantages

1. System calls only in the setup phase

Disadvantages

1. Explicit synchronization

2. Communication protocol & shared buffer management are the programmer's responsibility

Front 8

What is the end goal of both Message-passing IPC and Shared-memory IPC?

Back 8

Pass data from one address space into another address space

Front 9

Placeholder for Copy Vs Map

Back 9

write it

Front 10

Placeholder for Copy Vs Map

Back 10

write it

Front 11

In SysV Shared-Memory IPC, what is the key?

Back 11

An element assigned to a shared region of physical memory. This allows other processes to reference this memory segment using this key

Front 12

SysV Shared-Memory IPC placeholder

Back 12

Write it

Front 13

SysV Shared-Memory IPC placeholder

Back 13

Write it

Front 14

Regarding the SysV API, what do the following commands do?
shmget()

ftok()

shmat()

shmdt()

shmctl()

Back 14

shmget - Create or open shared memory

ftok() - Generates memory keys

shmat() - Attaches shared memory segment to process

shmdt() - Detaches a segment based on id

shmctl() - Passes a a control code to a shared memory segment

Front 15

Regarding the POSIX API, what do the following commands do?

shm_open()

mmap() and unmmap()

shm_close()

shm_unlink()

Back 15

Front 16

What is a difference between the POSIX Shared memory API and the SysV Shared memory API?

Back 16

The POSIX standard uses file descriptors instead of keys

Front 17

How do you perform IPC sync with Pthreads?

Back 17

Use PTHREAD_PROCESS_SHARED

Front 18

Click to see Pthreads IPC example C code

Back 18

Front 19

What are some other examples of IPC Synchronization?

Back 19

1. Message Queues

2. Semaphores

Front 20

Describe message queues

Back 20

1. Implement mutual exclusion via send/recv

Front 21

Describe Semaphores

Back 21

Operating System construct. Binary value that is similar to a mutex.

Value of 0, process is blocked

Value of 1, the value is decremented (locked) and process proceeds.