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Re: High CPU load on Postgres Server during Peak times!!!!

From: Andy Colson <andy(at)squeakycode(dot)net>
To: Shiva Raman <raman(dot)shivag(at)gmail(dot)com>, pgsql-performance(at)postgresql(dot)org
Subject: Re: High CPU load on Postgres Server during Peak times!!!!
Date: 2009-09-22 14:19:46
Message-ID: 4AB8DD02.7000202@squeakycode.net (view raw or flat)
Thread:
Lists: pgsql-performance
Shiva Raman wrote:
> Dear all
> 
>   I am having a problem of high cpu loads in my postgres server during 
> peak time. Following are the
> details of my setup (details as per the postgres wiki) .
> 
> 
> *Following is the output of TOP command during offpeak time.*
> 
> 
> top - 18:36:56 up 77 days, 20:33,  1 user,  load average: 12.99, 9.22, 10.37
> Tasks: 142 total,  12 running, 130 sleeping,   0 stopped,   0 zombie
> Cpu(s): 46.1%us,  1.9%sy,  0.0%ni,  6.1%id,  3.0%wa,  0.0%hi,  0.1%si, 
> 42.9%st
> Mem:  16133676k total, 13657396k used,  2476280k free,   450908k buffers
> Swap: 14466492k total,      124k used, 14466368k free, 11590056k cached
> 
>  PID USER      PR  NI  VIRT  RES  SHR S %CPU %MEM    TIME+  COMMAND     
>                                      
> 22458 postgres  19   0 2473m 477m 445m R   40  3.0   0:15.49 postmaster 
>                                        
> 22451 postgres  15   0 2442m 447m 437m S   33  2.8   0:30.44 postmaster 
>                                        
> 22464 postgres  17   0 2443m 397m 383m R   28  2.5   0:13.78 postmaster 
>                                        
> 22484 postgres  16   0 2448m 431m 412m S   20  2.7   0:02.73 postmaster 
>                                        
> 22465 postgres  17   0 2440m 461m 449m R   15  2.9   0:03.52 postmaster 
>                                        
> 22452 postgres  16   0 2450m 727m 706m R   13  4.6   0:23.46 postmaster 
>                                        
> 22476 postgres  16   0 2437m 413m 405m S   13  2.6   0:06.11 postmaster 
>                                        
> 22485 postgres  16   0 2439m 230m 222m R    7  1.5   0:05.72 postmaster 
>                                        
> 22481 postgres  15   0 2436m 175m 169m S    7  1.1   0:04.44 postmaster 
>                                        
> 22435 postgres  17   0 2438m 371m 361m R    6  2.4   1:17.92 postmaster 
>                                        
> 22440 postgres  17   0 2445m 497m 483m R    5  3.2   1:44.50 postmaster 
>                                        
> 22486 postgres  17   0 2432m  84m  81m R    4  0.5   0:00.76 postmaster 
>                                        


First off, nice report.

I see you are on a pretty old version of pg.  Are you vacuuming regularly?

If you run a 'ps ax|grep post' do you see anything that says 'idle in 
transaction'?  (I hope that old of version will show it.  my processes 
show up as postgres not postmaster)

The top looks like you are cpu bound.  Have you tried enabling logging 
slow queries? (again, I hope your version supports that)  It could be 
you have a query or two that are not using indexes, and slowing 
everything down.

Also on the top, it has this: 42.9%st.  Are you in a vm?  or running 
vm's on the box?

Its weird, you have 6.1% idle and 3.0% waiting for disk and yet you have 
a load of 13.  Load usually means somebody is waiting for something. 
But you have a little cpu idle time... and you have very low disk 
waits... you are using very little swap.  hum... odd...

-Andy

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Subject: Re: High CPU load on Postgres Server during Peak times!!!!
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