Re: Debugging infrequent pegged out CPU usage

From: Jason Long <mailing(dot)list(at)supernovasoftware(dot)com>
To: Scott Marlowe <scott(dot)marlowe(at)gmail(dot)com>
Cc: pgsql-general <pgsql-general(at)postgresql(dot)org>
Subject: Re: Debugging infrequent pegged out CPU usage
Date: 2008-11-03 19:59:15
Message-ID: 490F5813.5040807@supernovasoftware.com
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Scott Marlowe wrote:
> On Mon, Nov 3, 2008 at 12:25 PM, Scott Marlowe <scott(dot)marlowe(at)gmail(dot)com> wrote:
>
>> On Mon, Nov 3, 2008 at 11:30 AM, Jason Long
>> <mailing(dot)list(at)supernovasoftware(dot)com> wrote:
>>
>>> I am running PostgreSQL 8.3.4 on Centos 5.2 with a single Xeon 5472, 1600
>>> MHz, 12 MB cache, 3.0 GHz quad core, and 4 GB RAM.
>>>
>>> My database is only about 50 MB and there are only about 20 users.
>>>
>>> For some reason Postgres is pegging my CPU and I can barely log on to reboot
>>> the machine. After reboot all is well for another week or so, but this
>>> brings the system to a grinding halt.
>>>
>>> What is the best way to debug this?
>>> Can I limit Postgres to a certain number of cores or set the timeout on the
>>> queries to a lower value?
>>>
How about preventing this lockup by limiting CPU resources to Postgres
or giving up if a query takes too long? I am barely able to log in let
alone poke around.
>> Best way I've found it to keep track of the server over a period of
>> time. nagios and mrtg are your friends here.
>>
Thank you for the advice. I will investigate these options.
>> You can use some more primitive methods, like
>>
>> ps ax|grep postgres|wc -l
>>
>> to see how many postgres backends are running. You need to figure out
>> exactly what's happening to the machine before it dies, but as its
>> approaching that point.
>>
>
> Also, use the built in pg_xxx tables / views that show you what the
> server is doing.
>
> use vmstat, iostat, top and other tools to keep track. If you're on
> Windows, ignore all that and ask someone else cause I don't know
> enough about troubleshooting windows systems to be a lot of help
> there.
>

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