Re: postgres 9.3 vs. 9.4

----- Original Message -----
> From: "Merlin Moncure" <mmoncure(at)gmail(dot)com>
> To: "Tigran Mkrtchyan" <tigran(dot)mkrtchyan(at)desy(dot)de>
> Cc: "postgres performance list" <pgsql-performance(at)postgresql(dot)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(dot)mkrtchyan(at)desy(dot)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
>