Re: pg_test_fsync performance

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.

regards, tom lane