Skip to end of time quanta

Question

Is it possible to skip to the end of a process's allocated time-quantum? I have a program that works in parallel on a piece of shared memory, and then all of the processes need to wait for the others to finish and sync up before the next step. Each process will do a maximum of one iteration more than any other, so any timing differences are minimal.

microsleep almost works, but I'm pretty sure that even usleep(1) would take longer than I'd like (as of now I can do 5000 times through in about 1.5 seconds, so that would add around 20ms to a test).

Some kind of busy wait seems like a bad idea, though it's what I might end up going with.

What I would really like is something along the lines of

while(*everyoneDone != 0) {
    //give up rest of this time-quantum
}

It doesn't need to be realtime, it just needs to be fast. Any ideas?

Note that this will be run on a multiproc machine, because if there's only one core to work with, the existing single-threaded version is going to perform better.

Answer 1

You don't state what OS you're working with, but if it's POSIX then sched_yield() might be what you're looking for.

Really though, you'd almost certainly be better off using a proper synchronisation primitive, like a semaphore.

Answer 2

Don't do that, active waiting is almost always a bad idea in an application context. Use pthread_barrier_t, this is exactly the tool that is foreseen for your purpose.