From: Joshua D. Drake <jd@commandprompt.com>
To: josh@agliodbs.com
Cc: pgsql-performance@postgresql.org
Subject: Re: 2GB or not 2GB
Date: Thu, 29 May 2008 08:45:14 -0700
Message-ID: <1212075914.26576.8.camel@jd-laptop> (raw)
In-Reply-To: <200805281659.26945.josh@agliodbs.com>
References: <200805281659.26945.josh@agliodbs.com>
On Wed, 2008-05-28 at 16:59 -0700, Josh Berkus wrote:
> Folks,
> shared_buffers: according to witnesses, Greg Smith presented at East that
> based on PostgreSQL's buffer algorithms, buffers above 2GB would not
> really receive significant use. However, Jignesh Shah has tested that on
> workloads with large numbers of connections, allocating up to 10GB
> improves performance.
I have seen multiple production systems where upping the buffers up to
6-8GB helps. What I don't know, and what I am guessing Greg is referring
to is if it helps as much as say upping to 2GB. E.g; the scale of
performance increase goes down while the actual performance goes up
(like adding more CPUs).
>
> sort_mem: My tests with 8.2 and DBT3 seemed to show that, due to
> limitations of our tape sort algorithm, allocating over 2GB for a single
> sort had no benefit. However, Magnus and others have claimed otherwise.
> Has this improved in 8.3?
I have never see work_mem (there is no sort_mem Josh) do any good above
1GB. Of course, I would never willingly use that much work_mem unless
there was a really good reason that involved a guarantee of not calling
me at 3:00am.
>
> So, can we have some test evidence here? And workload descriptions?
>
Its all, tune now buddy :P
Sinceerely,
Joshua D. Drake
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To: pgsql-performance@postgresql.org
Cc: jd@commandprompt.com, josh@agliodbs.com
Subject: Re: 2GB or not 2GB
In-Reply-To: <1212075914.26576.8.camel@jd-laptop>
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