Re: postgres 9.3 vs. 9.4

On Thu, Sep 18, 2014 at 2:58 AM, Mkrtchyan, Tigran <tigran(dot)mkrtchyan(at)desy(dot)de
> wrote:

>
>
> Hi Folk,
>
> I am trying to investigate some performance issues which we have with
> postgres
> (a different topic by itself) and tried postgres.9.4beta2, with a hope
> that it
> perform better.
>
> Turned out that 9.4 is 2x slower than 9.3.5 on the same hardware.
>
> Some technical details:
>
> Host: rhel 6.5 2.6.32-431.23.3.el6.x86_64
> 256 GB RAM, 40 cores, Intel(R) Xeon(R) CPU E5-2660 v2 @ 2.20GHz
> 2x160GB PCIe SSD DELL_P320h-MTFDGAL175SAH ( on one 9.3, on an other one
> 9.4 )
>

Why are the versions segregated that way? Are you sure they are configured
identically?

>
> postgres tweaks:
>
>
> default_statistics_target = 100
> wal_writer_delay = 10s
> vacuum_cost_delay = 50
> synchronous_commit = off
>

Are you sure that synchronous_commit is actually off on the 9.4 instance?

9.3.5:
>
> # /usr/pgsql-9.3/bin/pgbench -r -j 1 -c 1 -T 60
>

...

> 0.035940 END;
>
>
> 9.4beta2:
>
...

> 0.957854 END;
>

Looks like IO.

Cheers,

Jeff