From: Mkrtchyan, Tigran <tigran.mkrtchyan@desy.de>
To: Mark Kirkwood <mark.kirkwood@catalyst.net.nz>
Cc: Merlin Moncure <mmoncure@gmail.com>
Cc: postgres performance list <pgsql-performance@postgresql.org>
Subject: Re: postgres 9.3 vs. 9.4
Date: Thu, 18 Sep 2014 23:10:54 +0200 (CEST)
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----- Original Message -----
> From: "Mark Kirkwood" <mark.kirkwood@catalyst.net.nz>
> To: "Merlin Moncure" <mmoncure@gmail.com>, "Tigran Mkrtchyan" <tigran.mkrtchyan@desy.de>
> Cc: "postgres performance list" <pgsql-performance@postgresql.org>
> Sent: Thursday, September 18, 2014 10:56:36 PM
> Subject: Re: [PERFORM] postgres 9.3 vs. 9.4
>
> 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.
10 minutes run had the same results.
Is there some kind of statistics which can tell there time is spend?
Or the only way is to run on solaris with dtrace? For me it's more important
to find why I get only 1500tps with 9.3. The test with 9.4 was just a hope for
a magic code change that will give me a better performance.
Tigran.
>
> > 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: tigran.mkrtchyan@desy.de, mark.kirkwood@catalyst.net.nz, mmoncure@gmail.com
Subject: Re: postgres 9.3 vs. 9.4
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