How do I make many system calls at once with the linux kernel?

Question

I was wondering if I could make a large number of system calls at the same time, with only one switch overhead. I need this because I have a need to make many (128) system calls at the same time. If I could do this without switching between kernel and userland 256+ times I think it could make my (speed sensitive) library significantly faster.

Answer 1

You really can't do that from an application program. What you could do is build a loadable kernel module that implements those operations and presents a simple API -- then you can change context once, do all the work, and return.

However, as with most of these sorts of optimization questions, the first thing to ask is "why do you think it's going to be necessary?" Do you have timing information etc? Have you profiled? How much of a performance issue do you really have, and is the additional complexity going to be worth the speedup?

Answer 2

I don't think Linux will support syscall chaining anytime soon. You might have more luck implementing this on another kernel and porting your application.

That said, it's not difficult to write a proxy to do the job in kernelspace for you, but don't expect it to be merged upstream. I've worked on real-time stuff and we had a solution like that, but never used in production because of support issues :/.