Date: Thu, 28 Nov 2019 17:23:19 -0500
From: Noah Misch <noah@leadboat.com>
To: Kyotaro Horiguchi <horikyota.ntt@gmail.com>
Cc: robertmhaas@gmail.com, pgsql-hackers@postgresql.org,
	9erthalion6@gmail.com, andrew.dunstan@2ndquadrant.com,
	hlinnaka@iki.fi, michael@paquier.xyz
Subject: Re: [HACKERS] WAL logging problem in 9.4.3?
Message-ID: <20191128222319.GA89611@gust.leadboat.com>
References: <20191125030839.GA51906@gust.leadboat.com>
 <20191126.213752.2132434859202124793.horikyota.ntt@gmail.com>
 <20191128.205620.2015649987051831334.horikyota.ntt@gmail.com>
 <20191128.213508.1108483203561250557.horikyota.ntt@gmail.com>
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On Thu, Nov 28, 2019 at 09:35:08PM +0900, Kyotaro Horiguchi wrote:
> I measured the performance with the latest patch set.
> 
> > 1. Determine $DDL_COUNT, a number of DDL transactions that take about one
> >    minute when done via syncs.
> > 2. Start "pgbench -rP1 --progress-timestamp -T180 -c10 -j10".
> > 3. Wait 10s.
> > 4. Start one DDL backend that runs $DDL_COUNT transactions.
> > 5. Save DDL start timestamp, DDL end timestamp, and pgbench output.

If you have the raw data requested in (5), please share them here so folks
have the option to reproduce your graphs and calculations.

> I did the following benchmarking.
> 
> 1. Initialize bench database
> 
>   $ pgbench -i -s 20
> 
> 2. Start server with wal_level = replica (all other variables are not
> changed) then run the attached ./bench.sh

The bench.sh attachment was missing; please attach it.  Please give the output
of this command:

  select name, setting from pg_settings where setting <> boot_val;

> 3. Restart server with wal_level = replica then run the bench.sh
> twice.

I assume this is wal_level=minimal, not wal_level=replica.