From: Mark Kirkwood <mark.kirkwood@catalyst.net.nz>
To: Merlin Moncure <mmoncure@gmail.com>
To: Mkrtchyan, Tigran <tigran.mkrtchyan@desy.de>
Cc: postgres performance list <pgsql-performance@postgresql.org>
Subject: Re: postgres 9.3 vs. 9.4
Date: Fri, 19 Sep 2014 08:56:36 +1200
Message-ID: <541B4704.9090305@catalyst.net.nz> (raw)
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On 19/09/14 08:32, Merlin Moncure wrote:
> 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?
>
Yes, does look suspicious. It *could* be that the 9.4 case is getting
unlucky and checkpointing just before the end of the 60s run, and 9.3
isn't.
> What is iowait? For pci-e SSD, these drives don't seem very fast...
>
>
>
These look like rebranded Micron P320's and should be extremely
fast...However I note that my Crucial/Micron M550's are very fast for
most writes *but* are much slower for sync writes (and fsync) that
happen at commit...
Cheers
Mark
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To: pgsql-performance@postgresql.org
Cc: mark.kirkwood@catalyst.net.nz, mmoncure@gmail.com, tigran.mkrtchyan@desy.de
Subject: Re: postgres 9.3 vs. 9.4
In-Reply-To: <541B4704.9090305@catalyst.net.nz>
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