From: ajaykbs <ajayakumarbs@gmail.com>
To: pgsql-performance@postgresql.org
Subject: Multi processor server overloads occationally with system process while running postgresql-9.4
Date: Sat, 3 Oct 2015 01:39:33 -0700 (MST)
Message-ID: <1443861573710-5868474.post@n5.nabble.com> (raw)
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I am working in a public company who uses only open source applications and
databases.I have a problem with our critical database which is write and
read intensive.*version:* Postgresql-9.4*Hardware:* HP DL980 (8-processor,
80 cores w/o hyper threading, 512GB RAM)*Operating system: *Red Hat
Enterprise Linux Server release 6.4 (Santiago)*uname -a* : Linux host1
2.6.32-358.el6.x86_64 #1 SMP Tue Jan 29 11:47:41 EST 2013 x86_64 x86_64
x86_64 GNU/LinuxSingle database with separate tablespace for main-data,
pg_xlog and indexesI have a database having 770GB size and expected to grow
to 2TB within the next year.The database was running in a 2processor HP
DL560 (16 cores) and as the transactions of the database were found
increasing, we have changed the hardware to DL980 with 8 processors and
512GB RAM. *Problem* It is observed that at some times during moderate load
the CPU usage goes up to 400% and the users are not able to complete the
queries in expected time. But the load is contributed by some system process
only.The average connections are normally 50. But when this happens the
connections will shoot up to max-connections.*The sar command
output*07:20:01 IST CPU %user %nice %system %iowait
%steal %idle07:30:01 IST all 0.73 0.00 0.37
0.58 0.00 98.3307:40:01 IST all 0.66 0.00 0.38
0.65 0.00 98.3107:50:01 IST all 0.27 0.00 0.27
0.01 0.00 99.4508:00:01 IST all 0.52 0.00 0.37
0.01 0.00 99.1008:10:01 IST all 1.54 0.00 0.70
0.02 0.00 97.7408:20:01 IST all 1.20 0.00 0.67
0.02 0.00 98.1008:30:01 IST all 1.48 0.00 0.77
0.03 0.00 97.7208:40:01 IST all 1.69 0.00 0.89
0.04 0.00 97.3908:50:01 IST all 1.71 0.00 0.94
0.04 0.00 97.3109:00:01 IST all 1.74 0.00 0.92
0.03 0.00 97.3109:10:01 IST all 2.32 0.00 1.06
0.04 0.00 96.5809:20:01 IST all 2.22 0.00 1.17
0.04 0.00 96.5709:30:02 IST all 2.20 0.00 6.68
0.06 0.00 91.0609:40:01 IST all 2.43 0.00 1.37
0.06 0.00 96.1409:50:01 IST all 3.23 0.00 2.06
0.08 0.00 94.6310:00:02 IST all 3.15 0.00 6.10
0.07 0.00 90.6710:10:01 IST all 4.94 0.00 5.20
0.29 0.00 89.5710:20:01 IST all 5.10 0.00 2.13
0.34 0.00 92.4310:30:01 IST all 5.60 0.00 2.42
0.18 0.00 91.8010:40:01 IST all 5.28 0.00 14.37
0.19 0.00 80.1610:50:01 IST all 4.52 0.00 28.48
0.23 0.00 66.7711:00:01 IST all 5.25 0.00 9.02
0.18 0.00 85.5511:10:01 IST all 5.77 0.00 4.96
0.27 0.00 89.0011:20:01 IST all 5.70 0.00 2.74
0.19 0.00 91.3711:30:01 IST all 5.72 0.00 5.91
0.20 0.00 88.1711:40:01 IST all 5.66 0.00 2.81
0.37 0.00 91.1511:50:01 IST all 5.90 0.00 8.80
0.10 0.00 85.1912:00:01 IST all 6.44 0.00 3.40
0.13 0.00 90.0312:10:01 IST all 7.18 0.00 4.52
0.11 0.00 88.1812:20:02 IST all 4.40 0.00 37.84
0.07 0.00 57.7012:30:01 IST all 5.66 0.00 2.98
0.10 0.00 91.2612:40:01 IST all 5.74 0.00 3.05
0.11 0.00 91.10Average: all 1.92 0.00 2.28
0.11 0.00 95.69Postgresql.confmax_connections = 500 (can be
reduced)shared_buffers = 8500MBwork_mem = 50MBmaintenance_work_mem =
8064MBcheckpoint_segments = 132checkpoint_timeout =
30mincheckpoint_completion_target = 0.9 This over load happens 5-6 times a
day.How to trace the cause of this problem?. My thoughts.1. some thing
related to the numa systems memory management.2. Some thing related to the
size of shared buffers.Please helpAjayakumar.BS
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To: pgsql-performance@postgresql.org
Cc: ajayakumarbs@gmail.com
Subject: Re: Multi processor server overloads occationally with system process while running postgresql-9.4
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