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Re: cpu utilization question

From: ries van Twisk <pg(at)rvt(dot)dds(dot)nl>
To: "Wright, George" <George(dot)Wright(at)infimatic(dot)com>
Cc: <pgsql-novice(at)postgresql(dot)org>
Subject: Re: cpu utilization question
Date: 2008-09-18 16:06:01
Message-ID: (view raw, whole thread or download thread mbox)
Lists: pgsql-novice
On Sep 18, 2008, at 10:59 AM, Wright, George wrote:

> We did profile the sql. The stand alone statements generally execute  
> in less than 30 ms. The clients (not browsers) send very short  
> delimited text messages to the server. The server parses them and  
> inserts a record for each message and only returns an HTTP 200, 400  
> to the client.
> I guess my confusion is why such a short message would cause  
> postmaster to use so much CPU. Several messages may arrive  
> simultaneously and that many postmasters get kicked off.
> We are currently installing the pgpool tool but I was wondering if  
> there were any other things I could try.

if a single SQL takes 30ms to insert... then I suspect it's a other PG  
process that takes up the CPU, may be a vacuum process?

> From: ries van Twisk [mailto:pg(at)rvt(dot)dds(dot)nl]
> Sent: Thursday, September 18, 2008 11:46 AM
> To: Wright, George
> Subject: Re: [NOVICE] cpu utilization question
> On Sep 18, 2008, at 10:09 AM, Wright, George wrote:
> We’re running Suse 10.2, PG 8.1.5, PHP 5.2.
> We’re seeing high CPU percentages for multiple instances of  
> postmaster: 15 – 30% for each instance. I realize a new instance is  
> spawned for each connection that is opened and we have lots of  
> clients sending very small text messages to our app for which we  
> record a row per message.
> We also have other periodic jobs that get kicked off but don’t use  
> near the cpu percentage that postmaster seems to.
> Is there a way to minimize postmaster’s cpu usage or is there some  
> way to share that process between requests?
> Thx.
> You could setup connection pooling for these clients (web clients I  
> assume),
> but be-careful with PHP Persistent connections... they are buggy...  
> I never used pgPool,
> but that might be something you need.
> When it comes to solving your high CPU processes you need to take a  
> look why it's slow.
> Use explain analyze as a start...
>                                                 regards, Ries van  
> Twisk
> -------------------------------------------------------------------------------------------------
> A: Because it messes up the order in which people normally read text.
> Q: Why is top-posting such a bad thing?
> A: Top-posting.
> Q: What is the most annoying thing in e-mail?

			regards, Ries van Twisk

Ries van Twisk
tags: Freelance TYPO3 Glassfish JasperReports JasperETL Flex Blaze-DS  
WebORB PostgreSQL DB-Architect
email: ries(at)vantwisk(dot)nl
skype: callto://r.vantwisk

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Subject: Moving data from one set of tables to another?
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