Re: 9.4 regression

On Wed, Aug 7, 2013 at 11:21 AM, Thom Brown <thom@linux.com> wrote:
> Hi all,
>
> I recently tried a simple benchmark to see how far 9.4 had come since
> 8.4, but I discovered that I couldn't get 9.4 to even touch 8.4 for
> performance.  After checking 9.2 and 9.3 (as per Kevin Grittner's
> suggestion), I found that those were fine, so the issue must be in
> 9.4devel.  I used identical configurations for each test, and used
> 9.1's pgbench to ensure changes in pgbench didn't affect the outcome.
>  The common config changes were:

...

> 8.4: 812.482108
> 9.4 HEAD: 355.397658
> 9.4 e5592c (9th July): 356.485625
> 9.4 537227 (7th July): 365.992518
> 9.4 9b2543 (7th July): 362.587339
> 9.4 269e78 (5th July): 359.439143
> 9.4 8800d8 (5th July): 821.933082
> 9.4 568d41 (2nd July): 822.991160
>
> 269e78 was the commit immediately after 8800d8, so it appears that
> introduced the regression.
>
> "Use posix_fallocate() for new WAL files, where available."
>
> Ironically, that was intended to be a performance improvement.

Would it be possible for you to download, compile, and run the test
program as described and located in this email:

http://www.postgresql.org/message-id/CAKuK5J1AcML-1cGBhnRzED-vh4oG+8HkmFhy2ECa-8JBJ-6qbQ@mail.gmail.com

I also wonder if there is a problem with the 3.8.0 kernel specifically.

-- 
Jon