pg.ddx.io  pgsql-performance@postgresql.org mailing list archive  

help / color / mirror / Atom feed
From: Tom Lane <tgl@sss.pgh.pa.us>
To: Craig James <craig_james@emolecules.com>
Cc: pgsql-performance@postgresql.org
Subject: Re: Occasional giant spikes in CPU load
Date: Fri, 25 Jun 2010 13:01:31 -0400
Message-ID: <6203.1277485291@sss.pgh.pa.us> (raw)
In-Reply-To: <4C24D679.7030701@emolecules.com>
References: <k2pda0294261004061437p9cd3810dqe9ce528b6ddb0873@mail.gmail.com>
	<m2m603c8f071004071413w1f2d2497hbbe07d9c6491848f@mail.gmail.com>
	<4BBCFB12.1010306@emolecules.com>
	<y2r72dbd3151004071556j22244233l8fa1db295b7f9cd3@mail.gmail.com>
	<r2q603c8f071004071747n3e56d12bo11c49885b8c2eb2e@mail.gmail.com>
	<4BBD3A17.90209@emolecules.com>
	<y2l72dbd3151004071950kfe09a98fqf0c9a136375260e2@mail.gmail.com>
	<v2u603c8f071004072007t323fe469lfdd8fa5f2a283890@mail.gmail.com>
	<4C23FD52.40508@emolecules.com>
	<23596.1277438692@sss.pgh.pa.us>
	<4C24B3BB.3070901@emolecules.com>
	<2286.1277477230@sss.pgh.pa.us>
	<4C24D679.7030701@emolecules.com>

Craig James <craig_james@emolecules.com> writes:
> On 6/25/10 7:47 AM, Tom Lane wrote:
>> Any chance of going to 8.4?  If this is what I suspect, you really need
>> this 8.4 fix:
>> http://archives.postgresql.org/pgsql-committers/2008-06/msg00227.php
>> which eliminated the thundering-herd behavior that previous releases
>> exhibit when the sinval queue overflows.

> Yes, there is a chance of upgrading to 8.4.4.  I just bought a new server and it has 8.4.4 on it, but it won't be online for a while so I can't compare yet.  This may motivate me to upgrade the current servers to 8.4.4 too.  I was pleased to see that 8.4 has a new upgrade-in-place feature that means we don't have to dump/restore.  That really helps a lot.

I wouldn't put a lot of faith in pg_migrator for an 8.3 to 8.4
conversion ... it might work, but test it on a copy of your DB first.
Possibly it'll actually be recommendable in 9.0.

> A question about 8.4.4: I've been having problems with bloat.  I thought I'd adjusted the FSM parameters correctly based on advice I got here, but apparently not.  8.4.4 has removed the configurable FSM parameters completely, which is very cool.  But ... if I upgrade a bloated database using the upgrade-in-place feature, will 8.4.4 recover the bloat and return it to the OS, or do I still have to recover the space manually (like vacuum-full/reindex, or cluster, or copy/drop a table)?

No, an in-place upgrade to 8.4 isn't magically going to fix that.  This
might actually be sufficient reason to stick with the tried&true dump
and reload method, since you're going to have to do something fairly
expensive anyway to clean out the bloat.

			regards, tom lane



view thread (31+ messages)

Message-ID: <6203.1277485291@sss.pgh.pa.us>
Permalink:  ../6203.1277485291@sss.pgh.pa.us/
Also on:    postgresql.org/message-id/6203.1277485291@sss.pgh.pa.us

 · 

reply
Reply instructions:

You may reply publicly to this message via plain-text email
using any one of the following methods:

* Reply to all the recipients using the --to and --cc options:
  reply via email

  To: pgsql-performance@postgresql.org
  Cc: tgl@sss.pgh.pa.us, craig_james@emolecules.com
  Subject: Re: Occasional giant spikes in CPU load
  In-Reply-To: <6203.1277485291@sss.pgh.pa.us>

* Save the following mbox file, import it into your mail client,
  and reply-to-all from there: mbox

This inbox is served by DDX for PostgreSQL; see mirroring instructions
for how to clone and mirror all data and code used for this inbox