Re: CPU usage when building a schema

Thank you for the feedback. I'll send Tom Lane an email. Do you think it would also be worth posting to the Admin or Performance lists?

-----Original Message-----
From: pgsql-novice-owner(at)postgresql(dot)org [mailto:pgsql-novice-owner(at)postgresql(dot)org] On Behalf Of Mladen Gogala
Sent: Wednesday, June 23, 2010 11:03 AM
To: Deborah Fuentes
Cc: Mladen Gogala; pgsql-novice(at)postgresql(dot)org; John Beckner
Subject: Re: [NOVICE] CPU usage when building a schema

Deborah, that is very strange. I would understand a CPU bound runaway
process but having 97 processes being ready to run simultaneously, thus
inundating the run queue seems like a bug. Tom Lane works for
EnterpriseDB, maybe he would know what
happens there. I don't have any Solaris available to test my hypothesis.
This definitely sounds like a platform specific bug.

Deborah Fuentes wrote:
> Mladen,
>
> Thank you for your reply. I apologize for not including the system specifics in my initial post.
>
> We are running Postgres 8.3.7 on a Sun M5000 with 2 x quad core CPUs (16 threads) running Solaris 10.
>
> When I run an SQL to create new tables and indexes is when Postgres consumes all CPU and impacts other users on the server.
>
> I've attached the sar data at the time of the run- here's a snip-it below.
>
> Thanks!
> Deb
>
> ****************************************************
>
> Here, note the run queue, the left column. That is the number of processes waiting to run. 97 processes waiting to run at any time with only eight CPU cores looks very busy.
>
> root(at)core2 # sar -q 5 500
>
> SunOS core2 5.10 Generic_142900-11 sun4u 06/17/2010
>
> 12:01:50 runq-sz %runocc swpq-sz %swpocc
> 12:01:55 1.8 80 0.0 0
> 12:02:00 1.0 20 0.0 0
> 12:02:05 1.0 20 0.0 0
> 12:02:10 0.0 0 0.0 0
> 12:02:15 0.0 0 0.0 0
> 12:02:21 3.3 50 0.0 0
> 12:02:26 1.0 20 0.0 0
> 12:02:31 1.0 60 0.0 0
> 12:02:36 1.0 20 0.0 0
> 12:02:42 27.0 50 0.0 0
> 12:02:49 32.8 83 0.0 0
> 12:02:55 76.0 100 0.0 0
> 12:03:01 66.1 100 0.0 0
> 12:03:07 43.8 100 0.0 0
> 12:03:13 52.0 100 0.0 0
> 12:03:19 91.2 100 0.0 0
> 12:03:26 97.8 83 0.0 0
> 12:03:33 63.7 100 0.0 0
> 12:03:39 67.4 100 0.0 0
> 12:03:47 41.5 100 0.0 0
> 12:03:53 82.0 83 0.0 0
> 12:03:59 88.7 100 0.0 0
> 12:04:06 87.7 50 0.0 0
> 12:04:12 41.3 100 0.0 0
> 12:04:17 94.3 50 0.0 0
> 12:04:22 1.0 20 0.0 0
> 12:04:27 3.3 60 0.0 0
> 12:04:32 1.0 20 0.0 0
> 12:04:38 0.0 0 0.0 0
>
> -----Original Message-----
> From: Mladen Gogala [mailto:mladen(dot)gogala(at)vmsinfo(dot)com]
> Sent: Wednesday, June 23, 2010 5:50 AM
> To: Deborah Fuentes
> Cc: pgsql-novice(at)postgresql(dot)org
> Subject: Re: [NOVICE] CPU usage when building a schema
>
> Deborah Fuentes wrote:
>
>> Hello,
>>
>>
>>
>> I'm new to Postgres so I apologize in advance for the simple question....
>>
>>
>>
>> Why is it when I'm building an empty schema does Postgres consume all
>> the CPU resources? My experience is with Informix and I've never seen
>> anything like this.
>>
>>
>>
>> Thanks!
>>
>> Deb
>>
>>
> What kind of a machine are you using? What OS, version and architecture?
> What Postgres version? If Linux, did you do "strace" to see what is
> going on? You can even compile PgSQL with the "-g" flag and use gprof
> to find out where the time is spent. Furthermore, what do you mean by
> "building an empty schema"? Are we talking about "create schema" command
> or something else? I tried creating an empty schema and it wasn't even
> visible on CPU:
> [mgogala(at)medo ~]$ psql
> Timing is on.
> psql (8.4.4)
> Type "help" for help.
>
> mgogala=# create schema test;
> CREATE SCHEMA
> Time: 192.082 ms
> mgogala=# drop schema test;
> DROP SCHEMA
> Time: 59.451 ms
> mgogala=#
>
> Simultaneously, in another window I did this:
> [mgogala(at)medo ~]$ sar -u 3 15
> Linux 2.6.18-194.3.1.el5.centos.plusPAE (medo) 06/23/2010
>
> 08:45:43 AM CPU %user %nice %system %iowait
> %steal %idle
> 08:45:46 AM all 3.00 0.00 0.83 1.50
> 0.00 94.68
> 08:45:49 AM all 2.17 0.00 0.67 0.00
> 0.00 97.16
> 08:45:52 AM all 2.16 0.00 1.00 0.00
> 0.00 96.84
> 08:45:55 AM all 2.50 0.00 1.50 3.00
> 0.00 93.01
> 08:45:58 AM all 2.34 0.00 0.33 0.00
> 0.00 97.33
> 08:46:01 AM all 0.67 0.00 0.50 1.00
> 0.00 97.83
>
> [mgogala(at)medo ~]$
>
> It didn't even make a ripple. My Postgres is 8.4.4, Linux is CentOS 5.5:
> mgogala(at)medo ~]$ uname -a
> Linux medo 2.6.18-194.3.1.el5.centos.plusPAE #1 SMP Wed May 19 10:00:02
> EDT 2010 i686 athlon i386 GNU/Linux
> [mgogala(at)medo ~]$
> What versions of OS and DB do you have? Do you have an OS or are you
> running Windows?
>
>
>
>

--

Mladen Gogala
Sr. Oracle DBA
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