Re: proposal: Set effective_cache_size to greater of .conf value, shared_buffers

From: Josh Berkus <josh(at)agliodbs(dot)com>
To: Merlin Moncure <mmoncure(at)gmail(dot)com>
Cc: PostgreSQL-development <pgsql-hackers(at)postgresql(dot)org>
Subject: Re: proposal: Set effective_cache_size to greater of .conf value, shared_buffers
Date: 2013-09-06 04:02:27
Message-ID: 522953D3.8040009@agliodbs.com
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On 09/05/2013 03:30 PM, Merlin Moncure wrote:

>> Standard advice we've given in the past is 25% shared buffers, 75%
>> effective_cache_size. Which would make EFS *3X* shared_buffers, not 4X.
>> Maybe we're changing the conventional calculation, but I thought I'd
>> point that out.
>
> This was debated upthread.

Actually, no, it wasn't. Tom threw out a suggestion that we use 4X for
historical reasons. That's all, there was no discussion.

So, my point stands: our historical advice has been to set EFS to 75% of
RAM. Maybe we're changing that advice, but if so, let's change it.
Otherwise 3X makes more sense.

--
Josh Berkus
PostgreSQL Experts Inc.
http://pgexperts.com

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