Re: pg_test_fsync performance

On Wed, Feb 15, 2012 at 01:35:05AM +0200, Marko Kreen wrote:
> On Tue, Feb 14, 2012 at 05:59:06PM -0500, Tom Lane wrote:
> > Bruce Momjian <bruce(at)momjian(dot)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.

Wow, I wasn't even aware this compiled in Win32; I thought it was
ifdef'ed out. Anyway, I am looking at SetTimer as a way of making this
work. (Me wonders if the GoGrid Windows images have compilers.)

I see backend/port/win32/timer.c so I might go with a simple "create a
thread, sleep(2), set flag, exit" solution.

--
Bruce Momjian <bruce(at)momjian(dot)us> http://momjian.us
EnterpriseDB http://enterprisedb.com

+ It's impossible for everything to be true. +