| From: | Jeff Janes <jeff(dot)janes(at)gmail(dot)com> |
|---|---|
| To: | Robert Haas <robertmhaas(at)gmail(dot)com> |
| Cc: | Sergey Koposov <koposov(at)ast(dot)cam(dot)ac(dot)uk>, Florian Pflug <fgp(at)phlo(dot)org>, Merlin Moncure <mmoncure(at)gmail(dot)com>, pgsql-hackers(at)postgresql(dot)org, Stephen Frost <sfrost(at)snowman(dot)net> |
| Subject: | Re: 9.2beta1, parallel queries, ReleasePredicateLocks, CheckForSerializableConflictIn in the oprofile |
| Date: | 2012-06-01 00:27:41 |
| Message-ID: | CAMkU=1x-52NUgR8eddo95DdB_Kt7vtfxtRByJ11mLxx7D0a1Pg@mail.gmail.com |
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On Thu, May 31, 2012 at 9:17 AM, Robert Haas <robertmhaas(at)gmail(dot)com> 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 just posted a patch under subject "pgbench--new transaction type"
that introduces a pgbench -P option.
I think that that would do a good job of simulating unique-key
look-ups on the inner side of a nested loop (which is basically what
we have here) and so creating contention on index pages. Right now I
don't have anything with more than 2 CPUs and 2 is not high enough to
get much contention so I can't post any meaningful numbers. (pgbench
-P might also be of interest in hash index investigation)
Cheers,
Jeff
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