Re: Timing overhead and Linux clock sources

On Mon, Aug 20, 2012 at 03:11:51PM -0400, Robert Haas wrote:
> On Thu, Aug 16, 2012 at 10:28 PM, Bruce Momjian <bruce(at)momjian(dot)us> wrote:
> > FYI, I am planning to go ahead and package this tool in /contrib for PG
> > 9.3.
>
> Isn't this exactly what we already did, in 9.2, in the form of
> contrib/pg_test_timing?

Sorry, not sure how I missed that commit. Anyway, I am attaching a
patch for 9.3 that I think improves the output of the tool, plus adds
some C comments.

The new output has the lowest duration times first:

Testing timing overhead for 3 seconds.
Per loop time including overhead: 41.31 nsec
Histogram of timing durations:
< usec % of total count
1 95.87135 69627856
2 4.12759 2997719
4 0.00086 628
8 0.00018 133
16 0.00001 5
32 0.00000 1

This should make the output clearer to eyeball for problems --- a good
timing has a high percentage on the first line, rather than on the last
line.

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

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