From: | Shane Ambler <pgsql(at)Sheeky(dot)Biz> |
---|---|
To: | Magnus Hagander <magnus(at)hagander(dot)net> |
Cc: | Andres Retzlaff <andres_retzlaff(at)hotmail(dot)com>, pgsql-performance(at)postgresql(dot)org |
Subject: | Re: Usage up to 50% CPU |
Date: | 2007-04-27 09:53:41 |
Message-ID: | 4631C825.9000705@Sheeky.Biz |
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Lists: | pgsql-performance |
Magnus Hagander wrote:
> On Fri, Apr 27, 2007 at 08:10:48AM +0000, Andres Retzlaff wrote:
>> Hi Magnus,
>>
>> in this case each CPU goes up to 50%, giveing me 50% total usage. I was
>> specting as you say 1 query 100% cpu.
>>
>> Any ideas?
>
> No. 1 query will only use 100% of *one* CPU, which means 50% total usage.
> You need at least one query per CPU to reach full 100% of the whole system.
> (Actually, you can get slightly above 50% since the query will run on one
> CPU and the OS and autovacuum and bgwriter can run on the other. But it's
> marginally)
>
> //Magnus
I would think that as you are sitting and watching the cpu usage, your
query would seem to taking a while to run, leading me to wonder if you
are getting a full table scan that is causing pg to wait for disk response?
Or are you running a long list of steps that take a while?
--
Shane Ambler
pgSQL(at)Sheeky(dot)Biz
Get Sheeky @ http://Sheeky.Biz
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