Skip site navigation (1) Skip section navigation (2)

Re: default resource limits

From: Andrew Dunstan <andrew(at)dunslane(dot)net>
To: daveg <daveg(at)sonic(dot)net>
Cc: "Patches (PostgreSQL)" <pgsql-patches(at)postgresql(dot)org>
Subject: Re: default resource limits
Date: 2005-12-23 23:20:06
Message-ID: 43AC8626.9060503@dunslane.net (view raw or flat)
Thread:
Lists: pgsql-hackerspgsql-patches

daveg wrote:

>On Fri, Dec 23, 2005 at 03:38:56PM -0500, Andrew Dunstan wrote:
>  
>
>>>What numbers would you like? If what I suggested seems odd, how about 
>>>targets of 400 connections, 4000 shared_buffers and 200,000 
>>>max_fsm_pages?
>>>      
>>>
>>Here's a patch that does what I had in mind. On my modest workstation it 
>>tops out at 400 connections and 2500/125000 
>>shared_buffers/max_fsm_pages. An idle postmaster with these settings 
>>consumed less than 4% of the 380Mb of memory, according to top, making 
>>it still dwarfed by X, mozilla, apache and amavisd among other memory hogs.
>>    
>>
>
>I don't understand the motivation for so many connections by default, it
>seems wasteful in most cases.
>
>
>  
>

The rationale is one connection per apache thread (which on Windows 
defaults to 400). If people think this is too many I could live with 
winding it back a bit - the defaults number of apache workers on Unix is 
250, IIRC.

Here's why iot matters: during Hurricane Katrina, one web site that was 
collecting details on people missing etc. found its application failing 
because apache/php wanted more connections (out of the box) than the out 
of the box postgres default. Luckily we were able to advise the operator 
on how to fix it very quickly, but having these in some sort of sync 
seems reasonable.

Of course, if you use connection pooling you can probably wind the 
number back  quite a lot.

There's no magic right answer - but on even entry level retail desktop 
machines the extra used from this is now quite a small drop in the 
memory bucket - the very lowest come with 256Mb of memory, and all but 
the very lowest come with 512Mb or 1Gb. So why should we argue over a 
handful of megabytes in raising limits last set 3 or 4 years ago?

cheers

andrew

In response to

Responses

pgsql-hackers by date

Next:From: Tom LaneDate: 2005-12-23 23:22:36
Subject: Re: default resource limits
Previous:From: Qingqing ZhouDate: 2005-12-23 23:00:37
Subject: Re: Questions related to xlog

pgsql-patches by date

Next:From: Tom LaneDate: 2005-12-23 23:22:36
Subject: Re: default resource limits
Previous:From: davegDate: 2005-12-23 22:22:56
Subject: Re: default resource limits

Privacy Policy | About PostgreSQL
Copyright © 1996-2014 The PostgreSQL Global Development Group