Re: postgres 9.3 vs. 9.4 - Mailing list pgsql-performance

----- Original Message -----
> From: "Merlin Moncure" <mmoncure@gmail.com>
> To: "Tigran Mkrtchyan" <tigran.mkrtchyan@desy.de>
> Cc: "postgres performance list" <pgsql-performance@postgresql.org>
> Sent: Thursday, September 18, 2014 10:32:20 PM
> Subject: Re: [PERFORM] postgres 9.3 vs. 9.4
>
> On Thu, Sep 18, 2014 at 4:58 AM, Mkrtchyan, Tigran
> <tigran.mkrtchyan@desy.de> wrote:
> >
> > 9.3.5:
> >         0.035940        END;
> >
> >
> > 9.4beta2:
> >         0.957854        END;
>
>
> time being spent on 'END' is definitely suggesting i/o related issues.
> This is making me very skeptical that postgres is the source of the
> problem.   I also thing synchronous_commit is not set properly on the
> new instance (or possibly there is a bug or some such).  Can you
> verify via:
>
> select * from pg_settings where name = 'synchronous_commit';
>
> on both servers?


here you are:

9.4beta2
postgres=# select version();
                                                     version
-----------------------------------------------------------------------------------------------------------------
 PostgreSQL 9.4beta2 on x86_64-unknown-linux-gnu, compiled by gcc (GCC) 4.4.7 20120313 (Red Hat 4.4.7-4), 64-bit
(1 row)

postgres=# select * from pg_settings where name = 'synchronous_commit';
        name        | setting | unit |          category          |                      short_desc
 | extra_desc | context | vartype |        
source       | min_val | max_val |          enumvals           | boot_val | reset_val |               sourcefile
       | sourceline  

--------------------+---------+------+----------------------------+-------------------------------------------------------+------------+---------+---------+-------

-------------+---------+---------+-----------------------------+----------+-----------+-----------------------------------------+------------
 synchronous_commit | off     |      | Write-Ahead Log / Settings | Sets the current transaction's synchronization
level.|            | user    | enum    | config 
uration file |         |         | {local,remote_write,on,off} | on       | off       |
/var/lib/pgsql/9.4/data/postgresql.conf|        622 
(1 row)


9.3.5
postgres=# select version();
                                                   version
--------------------------------------------------------------------------------------------------------------
 PostgreSQL 9.3.5 on x86_64-unknown-linux-gnu, compiled by gcc (GCC) 4.4.7 20120313 (Red Hat 4.4.7-4), 64-bit
(1 row)

postgres=# select * from pg_settings where name = 'synchronous_commit';
        name        | setting | unit |          category          |                      short_desc
 | extra_desc | context | vartype |        
source       | min_val | max_val |          enumvals           | boot_val | reset_val |               sourcefile
       | sourceline  

--------------------+---------+------+----------------------------+-------------------------------------------------------+------------+---------+---------+-------

-------------+---------+---------+-----------------------------+----------+-----------+-----------------------------------------+------------
 synchronous_commit | off     |      | Write-Ahead Log / Settings | Sets the current transaction's synchronization
level.|            | user    | enum    | config 
uration file |         |         | {local,remote_write,on,off} | on       | off       |
/var/lib/pgsql/9.3/data/postgresql.conf|        166 
(1 row)




>
> What is iowait?  For pci-e SSD, these drives don't seem very fast...

iostat, top and pg_top never show iowait greater than  0.7%

Tigran.

>
> merlin
>