Date: Mon, 14 May 2007 09:57:28 -0400 (EDT)
From: Greg Smith <gsmith@gregsmith.com>
To: pgsql-patches@postgresql.org
Subject: Re: Automatic adjustment of bgwriter_lru_maxpages
In-Reply-To: <46486705.3000507@enterprisedb.com>
Message-ID: <Pine.GSO.4.64.0705140946580.9478@westnet.com>
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On Mon, 14 May 2007, Heikki Linnakangas wrote:

> If it's safe to set it high, let's default it to infinity.

The maximum right now is 1000, and that would be a reasonable new default. 
You really don't to write more than 1000 per interval anyway without 
taking a break for checkpoints; the more writes you do at once, the higher 
the chances are you'll have the whole thing stall because the OS makes you 
wait for a write (this is not a theoretical comment; I've watched it 
happen when I try to get the BGW doing too much).

If someone has so much activity that they're allocating more than that 
during a period, they should shrink the delay instead.  The kinds of 
systems where 1000 isn't high enough for bgwriter_lru_maxpages are going 
to be compelled to adjust these parameters anyway for good performance.

--
* Greg Smith gsmith@gregsmith.com http://www.gregsmith.com Baltimore, MD