From: Mark Stosberg <mark@summersault.com>
To: pgsql-performance@postgresql.org
Subject: Re: Most effective tuning choices for busy website?
Date: Tue, 14 Jun 2005 17:34:52 -0500
Message-ID: <d8nlop$96e$1@sea.gmane.org> (raw)
References: <slrnd9s2n5.ca0.mark@simba.summersault.com>
<42A3AF2D.4000802@samurai.com>
Neil Conway wrote:
> Mark Stosberg wrote:
>> I've used PQA to analyze my queries and happy overall with how they are
>> running. About 55% of the query time is going to variations of the pet
>> searching query, which seems like where it should be going. The query is
>> frequent and complex. It has already been combed over for appropriate
>> indexing.
>
> It might be worth posting the EXPLAIN ANALYZE and relevant schema
> definitions for this query, in case there is additional room for
> optimization.
>
>> Our hardware: Dual 3 Ghz processors 3 GB RAM, running on FreeBSD.
>
> Disk?
>
> You are presumably using Xeon processors, right? If so, check the list
> archives for information on the infamous "context switching storm" that
> causes performance problems for some people using SMP Xeons.
I wanted to follow-up to report a positive outcome to tuning this Xeon
SMP machine on FreeBSD. We applied the following techniques, and saw the
average CPU usage drop by about 25%.
- in /etc/sysctl.conf, we set it to use raw RAM for shared memory:
kern.ipc.shm_use_phys=1
- We updated our kernel config and postmaster.conf to set
shared_buffers to about 8000.
- We disabled hyperthreading in the BIOS, which had a label like
"Logical Processors? : Disabled".
I recall there was tweak my co-worker made that's not on my list.
I realize it's not particularly scientific because we changed several things
at once...but at least it is working well enough for now.
Mark
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: mark@summersault.com
Subject: Re: Most effective tuning choices for busy website?
In-Reply-To: <d8nlop$96e$1@sea.gmane.org>
* 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