Re: XLogFlush invoked about twice as much after 9.2 group commit enhancement

From: Peter Geoghegan <pg(at)heroku(dot)com>
To: Jeff Janes <jeff(dot)janes(at)gmail(dot)com>
Cc: Amit Langote <amitlangote09(at)gmail(dot)com>, PostgreSQL-development <pgsql-hackers(at)postgresql(dot)org>
Subject: Re: XLogFlush invoked about twice as much after 9.2 group commit enhancement
Date: 2013-05-08 04:23:04
Message-ID: CAM3SWZS3OPaa=yCOmi4iXOSjktCN3g7Yx_itne68fMMNnQd9QA@mail.gmail.com
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On Tue, May 7, 2013 at 12:48 PM, Jeff Janes <jeff(dot)janes(at)gmail(dot)com> wrote:
> Anyway, I don't see this behavior change when turning on wal_debug and
> looking in the logfiles for 'xlog flush request' messages.

That could have everything to do with the hardware you're using. In
general, the higher the cost of an fsync, the more useful it is to
amortize that cost among concurrently committing transactions.

--
Peter Geoghegan

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