Question

Can anyone tell, how slow are the UNIX domain sockets, compared to Shared Memory (or the alternative memory-mapped file)?

Thanks.

Answer 1

It’s more a question of design, than speed (Shared Memory is faster), domain sockets are definitively more UNIX-style, and do a lot less problems. In terms of choice know beforehand:

Domain Sockets advantages

• blocking and non-blocking mode and switching between them
• you don’t have to free them when tasks are completed

Domain sockets disadvantages

• must read and write in a linear fashion

Shared Memory advantages

• non-linear storage
• will never block
• multiple programs can access it

Shared Memory disadvantages

• need locking implementation
• need manual freeing, even if unused by any program

That’s all I can think of now. However, I’d go with domain sockets any day — not to mention that it’s a lot easier then to reimplement them to do distributed computing. The speed gain of Shared Memory will be lost because of the need of a safe design. However, if you know exactly what you’re doing, and use the proper kernel calls, you can achieve greater speed with Shared Memory.