From: Tom Lane <tgl@sss.pgh.pa.us>
To: Josh Berkus <josh@agliodbs.com>
Cc: pgsql-performance@postgresql.org, Greg Smith <greg@2ndquadrant.com>
Subject: Re: Defaulting wal_sync_method to fdatasync on Linux for 9.1?
Date: Tue, 16 Nov 2010 20:22:08 -0500
Message-ID: <11497.1289956928@sss.pgh.pa.us> (raw)
In-Reply-To: <4CE32D36.5040902@agliodbs.com>
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Josh Berkus <josh@agliodbs.com> writes:
>> Well, we're not going to increase the default to gigabytes, but we could
>> very probably increase it by a factor of 10 or so without anyone
>> squawking. It's been awhile since I heard of anyone trying to run PG in
>> 4MB shmmax. How much would a change of that size help?
> Last I checked, though, this comes out of the allocation available to
> shared_buffers. And there definitely are several OSes (several linuxes,
> OSX) still limited to 32MB by default.
Sure, but the current default is a measly 64kB. We could increase that
10x for a relatively small percentage hit in the size of shared_buffers,
if you suppose that there's 32MB available. The current default is set
to still work if you've got only a couple of MB in SHMMAX.
What we'd want is for initdb to adjust the setting as part of its
probing to see what SHMMAX is set to.
regards, tom lane
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To: pgsql-performance@postgresql.org
Cc: tgl@sss.pgh.pa.us, josh@agliodbs.com, greg@2ndquadrant.com
Subject: Re: Defaulting wal_sync_method to fdatasync on Linux for 9.1?
In-Reply-To: <11497.1289956928@sss.pgh.pa.us>
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