Re: postgres 9.3 vs. 9.4

On Fri, Sep 19, 2014 at 6:58 PM, Mark Kirkwood
<mark(dot)kirkwood(at)catalyst(dot)net(dot)nz> wrote:
> On 19/09/14 19:24, Mkrtchyan, Tigran wrote:
>>
>>
>>
>> ----- Original Message -----
>>>
>>> From: "Mark Kirkwood" <mark(dot)kirkwood(at)catalyst(dot)net(dot)nz>
>>> To: "Tigran Mkrtchyan" <tigran(dot)mkrtchyan(at)desy(dot)de>
>>> Cc: "Merlin Moncure" <mmoncure(at)gmail(dot)com>, "postgres performance list"
>>> <pgsql-performance(at)postgresql(dot)org>
>>> Sent: Friday, September 19, 2014 8:26:27 AM
>>> Subject: Re: [PERFORM] postgres 9.3 vs. 9.4
>>>
>>> On 19/09/14 17:53, Mkrtchyan, Tigran wrote:
>>>>
>>>>
>>>>
>>>> ----- Original Message -----
>>>>>
>>>>> From: "Mark Kirkwood" <mark(dot)kirkwood(at)catalyst(dot)net(dot)nz>
>>>
>>>
>>>>> Further to the confusion, here's my 9.3 vs 9.4 on two M550 (one for 9.3
>>>>> one for 9.4), see below for results.
>>>>>
>>>>> I'm running xfs on them with trim/discard enabled:
>>>>>
>>>>> $ mount|grep pg
>>>>> /dev/sdd4 on /mnt/pg94 type xfs (rw,discard)
>>>>> /dev/sdc4 on /mnt/pg93 type xfs (rw,discard)
>>>>>
>>>>>
>>>>> I'm *not* seeing any significant difference between 9.3 and 9.4, and
>>>>> the
>>>>> numbers are both about 2x your best number, which is food for thought
>>>>> (those P320's should toast my M550 for write performance...).
>>>>
>>>>
>>>> cool! any details on OS and other options? I still get the same numbers
>>>> as before.
>>>>
>>>
>>> Sorry, Ubuntu 14.04 on a single socket i7 3.4 Ghz, 16G (i.e my
>>> workstation).
>>>
>>> I saw the suggestion that Didier made to run 9.3 on the SSD that you
>>> were using for 9.4, and see if it suddenly goes slow - then we'd know
>>> it's something about the disk (or filesystem/mount options). Can you
>>> test this?
>>
>>
>>
>> swapping the disks did not change the results.
>>
>>
>
> Do you mean that 9.3 was still faster using the disk that 9.4 had used? If
> so that strongly suggests that there is something you have configured
> differently in the 9.4 installation [1]. Not wanting to sound mean - but it
> is really easy to accidentally connect to the wrong instance when there are
> two on the same box (ahem, yes , done it myself). So perhaps another look at
> the 9.4 vs 9.3 setup (or even posti the config files postgresql.conf +
> postgresql.auto.conf for 9.4 here).

Huh. Where did the 9.4 build come from? I wonder if there are some
debugging options set. Can you check 9.4 pg_settings for value
of"debug_assertions"? If it's set true, you might want to consider
hand compiling postgres until 9.4 is released...

merlin