From: | Tom DalPozzo <t(dot)dalpozzo(at)gmail(dot)com> |
---|---|
To: | Tomas Vondra <tomas(dot)vondra(at)2ndquadrant(dot)com> |
Cc: | Adrian Klaver <adrian(dot)klaver(at)aklaver(dot)com>, pgsql-general <pgsql-general(at)postgresql(dot)org> |
Subject: | Re: INSERT - UPDATE throughput oscillating and SSD activity after stopping the client |
Date: | 2016-12-05 15:52:25 |
Message-ID: | CAK77FCSvoHKVSAqKUdbe5AWM4TZ9Qry3DTvPZ_svdMFn-VefNw@mail.gmail.com |
Views: | Raw Message | Whole Thread | Download mbox | Resend email |
Thread: | |
Lists: | pgsql-general |
I tried to tune some parameters without appreciable changes in this
behaviour.
I tried to play with:
checkpoint timeout
wal size
shared buffers
commit delay
checkpoijnt completion target
No meaningful info found in the log file.
Regards
2016-12-04 4:02 GMT+01:00 Tomas Vondra <tomas(dot)vondra(at)2ndquadrant(dot)com>:
> On Fri, 2016-12-02 at 13:45 -0800, Adrian Klaver wrote:
> >
> > On 12/02/2016 09:40 AM, Tom DalPozzo wrote:
> > >
> > >
> > > Hi,
> > > I've two tables, t1 and t2, both with one bigint id indexed field
> > > and
> > > one 256 char data field; t1 has always got 10000 row, while t2 is
> > > increasing as explained in the following.
> > >
> > > My pqlib client countinously updates one row in t1 (every time
> > > targeting a different row) and inserts a new row in t2. All this in
> > > blocks of 1000 update-insert per commit, in order to get better
> > > performance.
> > > Wal_method is fsync, fsync is on, attached my conf file.
> > > I've a 3.8ghz laptop with evo SSD.
> > >
> > > Performance is measured every two executed blocks and related to
> > > these
> > > blocks.
> > >
> > > Over the first few minutes performance is around 10Krow/s then it
> > > slowly
> > > drops, over next few minutes to 4Krow/s, then it slowly returns
> > > high and
> > > so on, like a wave.
> > > I don't understand this behaviour. Is it normal? What does it
> > > depend on?
> > Have you looked at the Postgres log entries that cover these
> > episodes?
> >
> > Is there anything of interest there?
> >
> In particular look at checkpoints. In the config file you've changed
> checkpoint_timeout, but you haven't changed max_wal_size, so my guess
> is the checkpoints happen every few minutes, and run for about 1/2 the
> time (thanks for completion_target=0.5). That would be consistent with
> pattern of good/bad performance.
>
> regards
>
> --
> Tomas Vondra http://www.2ndQuadrant.com
> PostgreSQL Development, 24x7 Support, Remote DBA, Training & Services
> --
> Tomas Vondra http://www.2ndQuadrant.com
> PostgreSQL Development, 24x7 Support, Remote DBA, Training & Services
>
>
From | Date | Subject | |
---|---|---|---|
Next Message | basti | 2016-12-05 15:55:53 | Re: Postgres Traffic accounting |
Previous Message | basti | 2016-12-05 15:23:10 | Re: Postgres Traffic accounting |