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Re: auto-sizing wal_buffers

From: Fujii Masao <masao(dot)fujii(at)gmail(dot)com>
To: Josh Berkus <josh(at)agliodbs(dot)com>
Cc: Greg Smith <greg(at)2ndquadrant(dot)com>, Tom Lane <tgl(at)sss(dot)pgh(dot)pa(dot)us>, Robert Haas <robertmhaas(at)gmail(dot)com>, Magnus Hagander <magnus(at)hagander(dot)net>, pgsql-hackers(at)postgresql(dot)org
Subject: Re: auto-sizing wal_buffers
Date: 2011-01-17 01:15:46
Message-ID: (view raw or whole thread)
Lists: pgsql-hackers
On Sun, Jan 16, 2011 at 7:34 AM, Josh Berkus <josh(at)agliodbs(dot)com> wrote:
> I think we can be more specific on that last sentence; is there even any
> *theoretical* benefit to settings above 16MB, the size of a WAL segment?
>  Certainly there have been no test results to show any.

If the workload generates 16MB or more WAL for wal_writer_delay,
16MB or more of wal_buffers would be effective. In that case,
wal_buffers is likely to be filled up with unwritten WAL, then you have
to write buffers while holding WALInsert lock. This is obviously not


Fujii Masao
NTT Open Source Software Center

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