From: Alvaro Herrera <alvherre@commandprompt.com>
To: Tom Lane <tgl@sss.pgh.pa.us>
Cc: Greg Stark <gsstark@mit.edu>
Cc: Pierre C <lists@peufeu.com>
Cc: Greg Smith <greg@2ndquadrant.com>
Cc: Dave Crooke <dcrooke@gmail.com>
Cc: Paul McGarry <paul@paulmcgarry.com>
Cc: pgsql-performance@postgresql.org
Subject: Re: shared_buffers advice
Date: Tue, 16 Mar 2010 18:49:03 -0300
Message-ID: <20100316214903.GH3037@alvh.no-ip.org> (raw)
In-Reply-To: <15102.1268775566@sss.pgh.pa.us>
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Tom Lane escribió:
> Alvaro Herrera <alvherre@commandprompt.com> writes:
> > Maybe it would make more sense to try to reorder the fsync calls
> > instead.
>
> Reorder to what, though? You still have the problem that we don't know
> much about the physical layout on-disk.
Well, to block numbers as a first step.
However, this reminds me that sometimes we take the block-at-a-time
extension policy too seriously. We had a customer that had a
performance problem because they were inserting lots of data to TOAST
tables, causing very frequent extensions. I kept wondering whether an
allocation policy that allocated several new blocks at a time could be
useful (but I didn't try it). This would also alleviate fragmentation,
thus helping the physical layout be more similar to logical block
numbers.
--
Alvaro Herrera http://www.CommandPrompt.com/
PostgreSQL Replication, Consulting, Custom Development, 24x7 support
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Cc: alvherre@commandprompt.com, tgl@sss.pgh.pa.us, gsstark@mit.edu, lists@peufeu.com, greg@2ndquadrant.com, dcrooke@gmail.com, paul@paulmcgarry.com
Subject: Re: shared_buffers advice
In-Reply-To: <20100316214903.GH3037@alvh.no-ip.org>
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