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Re: oom_killer

From: Scott Marlowe <scott(dot)marlowe(at)gmail(dot)com>
To: Tory M Blue <tmblue(at)gmail(dot)com>
Cc: Claudio Freire <klaussfreire(at)gmail(dot)com>, pgsql-performance(at)postgresql(dot)org
Subject: Re: oom_killer
Date: 2011-04-21 20:04:00
Message-ID: BANLkTikb_HK9vGbkO04imFxL9Awt0Wsnzg@mail.gmail.com (view raw or flat)
Thread:
Lists: pgsql-performance
On Thu, Apr 21, 2011 at 11:15 AM, Tory M Blue <tmblue(at)gmail(dot)com> wrote:

> While I don't mind the occasional slap of reality. This configuration
> has run for 4+ years. It's possible that as many other components each
> fedora release is worse then the priors.

How many of those 300 max connections do you generally use?  If you've
always used a handful, or you've used more but they weren't memory
hungry then you've been lucky.

work_mem is how much memory postgresql can allocate PER sort or hash
type operation.  Each connection can do that more than once.  A
complex query can do it dozens of times.  Can you see that going from
20 to 200 connections and increasing complexity can result in memory
usage going from a few megabytes to something like 200 connections *
100Megabytes per sort * 3 sorts = 60Gigabytes.

> The Os has changed 170 days ago from fc6 to f12, but the postgres
> configuration has been the same, and umm no way it can operate, is so
> black and white, especially when it has ran performed well with a
> decent sized data set for over 4 years.

Just because you've been walking around with a gun pointing at your
head without it going off does not mean walking around with a gun
pointing at your head is a good idea.

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Subject: Re: oom_killer
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Subject: Re: Constraint exclusion can't process simple constant expressions?

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