AW: AW: Re[4]: Allowing WAL fsync to be done via O_SYNC

> >> It's great as long as you never block, but it sucks for making things
> >> wait, because the wait interval will be some multiple of 10 msec rather
> >> than just the time till the lock comes free.
> 
> > On the AIX platform usleep (3) is able to really sleep microseconds without 
> > busying the cpu when called for more than approx. 100 us (the longer the interval,
> > the less busy the cpu gets) .
> > Would this not be ideal for spin_lock, or is usleep not very common ?
> > Linux sais it is in the BSD 4.3 standard.
> 
> HPUX has usleep, but the man page says
> 
>      The usleep() function is included for its historical usage. The
>      setitimer() function is preferred over this function.

I doubt that setitimer has microsecond precision on HPUX.

> In any case, I would expect that all these functions offer accuracy
> no better than the scheduler's regular clock cycle (~ 100Hz) on most
> kernels.

Not on AIX, and I don't beleive that for the majority of other UNIX platforms eighter. 
I do however suspect, that some implementations need a busy loop, which would, 
if at all, only be acceptable on an SMP system.

Andreas