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Re: [PATCHES] default resource limits

From: Andrew Dunstan <andrew(at)dunslane(dot)net>
To: PostgreSQL-development <pgsql-hackers(at)postgresql(dot)org>
Subject: Re: [PATCHES] default resource limits
Date: 2005-12-26 18:08:02
Message-ID: 43B03182.7010004@dunslane.net (view raw or flat)
Thread:
Lists: pgsql-hackerspgsql-patches
I wrote:

>Tom Lane said:
>  
>
>>I think this probably needs to be more aggressive
>>though.  In a
>>situation of limited SHMMAX it's probably more important to keep
>>shared_buffers as high as we can than to get a high max_connections. We
>>could think about increasing the 5x multiplier, adding Min and/or Max
>>limits, or some combination.
>>
>>    
>>
>
>Yes. If we were to base it on the current maxima (1000/100), we could use a
>factor of 10, or if on the maxima I am now proposing (4000/250) a factor of
>16. Something in that range is about right I suspect.
>
>
>  
>

In experimenting I needed to set this at 20 for it to bite much. If we 
wanted to fine tune it I'd be inclined to say that we wanted 
20*connections buffers for the first, say, 50  or 100 connections and 10 
or 16 times for each connection over that. But that might be getting a 
little too clever - something we should leave to a specialised tuning 
tool. After all, we try these in fairly discrete jumps anyway. Maybe a 
simple factor around 20 would be sufficient.

Leaving aside the question of max_connections, which seems to be the 
most controversial, is there any objection to the proposal to increase 
the settings tried for shared_buffers (up to 4000) and max_fsm_pages (up 
to 200000) ? If not, I'll apply a patch for those changes shortly.

cheers

andrew

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