Re: Extremely high CPU usage when building tables

We did see a small spike in disk I/O, but only had wait I/O for less than 10 seconds total. The low CPU idle event goes on for several minutes, wait I/O or heavier I/O does not correlate to the extended period.

System time does jump up at the same time as the user time. System times of 15% when CPU us at 60% (25% idle) is around the average for this test. We believe that jump is related to showing time spent getting processes on and off CPU to execute. No general system wait I/O is observed during this time.

Five second samples of the Fiber disk SAN volumes. Wait I/O is listed in red. Note it's ten seconds or less.

extended device statistics
r/s w/s Mr/s Mw/s wait actv wsvc_t asvc_t %w %b device
1.0 296.9 0.0 136.5 0.0 62.3 0.0 209.0 0 168 c3
0.0 11.4 0.0 0.1 0.0 0.5 0.0 41.6 0 30 c3t60A98000572D4275684A563761586D71d0
0.4 28.0 0.0 0.9 0.0 3.0 0.0 104.4 0 41 c3t60A98000572D4275684A5638364D644Ed0
0.6 257.5 0.0 135.6 0.0 58.8 0.0 227.9 0 98 c3t60A98000572D4275684A56385468434Fd0
extended device statistics
r/s w/s Mr/s Mw/s wait actv wsvc_t asvc_t %w %b device
13.8 721.2 0.1 133.9 0.0 75.0 0.0 102.0 0 200 c3
0.0 88.8 0.0 6.0 0.0 19.0 0.0 213.7 0 65 c3t60A98000572D4275684A563761586D71d0
2.4 86.6 0.0 1.2 0.0 1.6 0.0 18.0 0 39 c3t60A98000572D4275684A5638364D644Ed0
11.4 545.8 0.1 126.7 0.0 54.4 0.0 97.7 0 97 c3t60A98000572D4275684A56385468434Fd0
extended device statistics
r/s w/s Mr/s Mw/s wait actv wsvc_t asvc_t %w %b device
3.6 769.0 0.0 123.2 29.4 182.9 38.1 236.7 5 220 c3
0.0 104.2 0.0 1.4 0.0 34.3 0.0 329.0 0 46 c3t60A98000572D4275684A563761586D71d0
1.0 77.0 0.0 13.1 0.0 8.1 0.0 103.2 0 77 c3t60A98000572D4275684A5638364D644Ed0
2.6 587.8 0.0 108.8 29.4 140.5 49.9 238.0 41 98 c3t60A98000572D4275684A56385468434Fd0
extended device statistics
r/s w/s Mr/s Mw/s wait actv wsvc_t asvc_t %w %b device
9.4 761.2 0.1 133.1 3.3 122.6 4.3 159.1 1 196 c3
0.0 33.8 0.0 0.3 0.0 2.1 0.0 63.5 0 30 c3t60A98000572D4275684A563761586D71d0
7.4 94.8 0.1 1.8 0.0 16.2 0.0 158.6 0 66 c3t60A98000572D4275684A5638364D644Ed0
2.0 632.6 0.0 131.0 3.3 104.3 5.2 164.3 10 99 c3t60A98000572D4275684A56385468434Fd0
extended device statistics
r/s w/s Mr/s Mw/s wait actv wsvc_t asvc_t %w %b device
2.8 588.2 0.0 126.0 0.0 112.6 0.0 190.5 0 239 c3
0.0 25.0 0.0 0.2 0.0 1.8 0.0 72.3 0 52 c3t60A98000572D4275684A563761586D71d0
0.0 157.4 0.0 12.0 0.0 10.7 0.2 68.0 0 87 c3t60A98000572D4275684A5638364D644Ed0
2.8 405.8 0.0 113.8 0.0 100.1 0.0 244.9 0 100 c3t60A98000572D4275684A56385468434Fd0

Thanks!
Deb

From: Rajesh Kumar Mallah [mailto:mallah(dot)rajesh(at)gmail(dot)com]
Sent: Thursday, July 01, 2010 2:50 AM
To: Deborah Fuentes
Cc: pgsql-performance(at)postgresql(dot)org
Subject: Re: [PERFORM] Extremely high CPU usage when building tables

Hi,

1. Did you also check vmstat output , from sar output the i/o wait is not clear.
2. i gues you must be populating the database between creating tables and creating
indexes. creating indexes require sorting of data that may be cpu intensive, loading/populating
the data may saturate the i/o bandwidth . I think you should check when the max cpu utilisation
is taking place exactly.

regds
Rajesh Kumar Mallah.
On Sat, Jun 26, 2010 at 3:55 AM, Deborah Fuentes <dfuentes(at)eldocomp(dot)com<mailto:dfuentes(at)eldocomp(dot)com>> wrote:
Hello,

When I run an SQL to create new tables and indexes is when Postgres consumes all CPU and impacts other users on the server.

We are running Postgres 8.3.7 on a Sun M5000 with 2 x quad core CPUs (16 threads) running Solaris 10.

I've attached the sar data at the time of the run- here's a snip-it below.

Any ideas would be greatly appreciated.

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

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