Re: Instrument checkpoint sync calls

Robert Haas <robertmhaas@gmail.com> writes:
> I would be very surprised if we can find a system where gettimeofday()
> takes a significant amount of time compared with fsync().  It might be
> (probably is) too expensive to stick into code paths that are heavily
> CPU-bounded, but surely the cost here is going to be dwarfed by the
> fsync(), no?  Unless maybe there's no I/O to be done anyway, but that
> case doesn't seem important to optimize for.

I'm not sure I buy that --- the whole point of spread checkpoints is
that we hope the I/O happens before we actually call fsync.

> Making it
> conditional on log_checkpoints seems entirely sufficient to me.

But I'll agree with that.  If you're turning on log_checkpoints then
you've given the system permission to indulge in extra overhead for
monitoring.
        regards, tom lane