Date: Wed, 26 Sep 2018 15:05:00 -0500
From: Justin Pryzby <pryzby@telsasoft.com>
To: pgsql-performance@postgresql.org
Subject: reference regarding write load during different stages of checkpoint
Message-ID: <20180926200500.GA493@telsasoft.com>
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I'm hoping to find a document I once read about the write load.

As best I can recall, it looked something like this:

. at beginning of (spread) checkpoint, larger than average write load to
  pg_wal/, due to full_page_writes;
. during most of checkpoint, decreasing WAL due to FPW, 
. towards end of checkpoint, increased writes to table data base/, due to
  fsync();
. assuming the next checkpoint doesn't start immediately, quiescent period, due
  to clean OS buffers;

This isn't very important, but I hadn't seen that described before, and 
I think there was more detail than I can remember.

I've been hoping for awhile to run across it and not able to find it.  It
probably dates back to 8.3/9.0 days and maybe disappeared.

Does anyone know what I'm talking about or where I can find it?

Thanks,
Justin