Re: 9.2beta1, parallel queries, ReleasePredicateLocks, CheckForSerializableConflictIn in the oprofile

On Thu, 31 May 2012, Robert Haas wrote:

> Oh, ho. So from this we can see that the problem is that we're
> getting huge amounts of spinlock contention when pinning and unpinning
> index pages.
>
> It would be nice to have a self-contained reproducible test case for
> this, so that we could experiment with it on other systems.

I have created it a few days ago:
http://archives.postgresql.org/pgsql-hackers/2012-05/msg01143.php

It is still valid. And I'm using exactly it to test. The only thing to
change is to create a two-col index and drop another index.
The scripts are precisely the ones I'm using now.

The problem is that in order to see a really big slowdown (10 times slower
than a single thread) I've had to raise the buffers to 48g but it was
slow for smaller shared buffer settings as well.

But I'm not sure how sensitive the test is to the hardware.

Cheers,
S

*****************************************************
Sergey E. Koposov, PhD, Research Associate
Institute of Astronomy, University of Cambridge
Madingley road, CB3 0HA, Cambridge, UK Tel: +44-1223-337-551
Web: http://www.ast.cam.ac.uk/~koposov/