Re: pg_test_fsync performance

On Tue, Feb 14, 2012 at 05:59:06PM -0500, Tom Lane wrote:
> Bruce Momjian <bruce@momjian.us> writes:
> > On Mon, Feb 13, 2012 at 08:28:03PM -0500, Tom Lane wrote:
> >> +1, I was about to suggest the same thing.  Running any of these tests
> >> for a fixed number of iterations will result in drastic degradation of
> >> accuracy as soon as the machine's behavior changes noticeably from what
> >> you were expecting.  Run them for a fixed time period instead.  Or maybe
> >> do a few, then check elapsed time and estimate a number of iterations to
> >> use, if you're worried about the cost of doing gettimeofday after each
> >> write.
> 
> > Good idea, and it worked out very well.  I changed the -o loops
> > parameter to -s seconds which calls alarm() after (default) 2 seconds,
> > and then once the operation completes, computes a duration per
> > operation.
> 
> I was kind of wondering how portable alarm() is, and the answer
> according to the buildfarm is that it isn't.

I'm using following simplistic alarm() implementation for win32:

  https://github.com/markokr/libusual/blob/master/usual/signal.c#L21

this works with fake sigaction()/SIGALARM hack below - to remember
function to call.

Good enough for simple stats printing, and avoids win32-specific
code spreading around.

-- 
marko