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To: pgsql-admin@postgresql.org <pgsql-admin@postgresql.org>
Subject: Large memory machine and PG 9.2.9
Date: Tue, 24 Feb 2015 21:19:59 +0100
Message-ID: <fa77ad64f4b8bd5f0f5f0a1ef5dd9871.squirrel@shrek.krogh.cc> (raw )
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Hi.
We have just moved our 9.2.9 instance onto new beefy iron. The machine has
48 Intel cores and 3TB of memory. Running linux 3.13.0-43 (Ubuntu 12.04).
The problem is a bit hard to describe, but I do suspect it is related to
the large memory and probably kernel og pg-kernel interaction.
Performance is nice up and until the point where the memory is full at
which point sluggish behaviour comes up. sar -B output is.
17:30:01 29513.79 140026.51 634164.09 0.00 160093.42 0.00
0.00 0.00 0.00
17:35:01 31351.13 154801.18 638880.17 0.12 184323.22 0.00
0.00 0.00 0.00
17:40:01 38269.69 128701.23 652375.35 0.23 176369.40 0.00
0.00 0.00 0.00
17:45:01 34834.14 135371.82 627765.26 0.00 169779.58 0.00
0.00 0.00 0.00
17:50:01 34039.17 134630.64 627500.30 0.00 174259.04 0.00
0.00 0.00 0.00
17:55:01 30318.70 150791.13 612534.75 0.00 163425.51 0.00
0.00 0.00 0.00
18:05:01 28446.80 122103.38 549891.01 0.26 141756.52 0.00
612.77 556.60 90.83
18:10:01 12944.16 39222.64 332848.27 4.27 82317.48 0.00
3037.11 2725.14 89.73
18:15:01 12955.10 47841.51 453714.33 3.95 106397.71 1018.39
4811.64 5421.81 93.00
18:20:01 16393.43 64063.10 548341.21 2.48 149489.93 6447.13
2238.06 8537.87 98.30
18:25:01 15725.89 59096.20 502043.56 0.27 152932.96 5197.78
2783.81 7782.02 97.50
18:30:01 12735.95 50460.08 394507.90 0.09 143488.71 4645.20
2141.35 6621.27 97.56
18:35:01 11995.37 52743.57 414669.31 0.02 134363.87 5096.32
1708.52 6668.57 98.00
18:40:01 11448.30 43185.84 373441.27 0.35 109712.93 3247.41
1772.93 4902.79 97.66
18:45:01 10959.95 44993.48 402033.19 0.04 115914.63 3157.24
2393.26 5378.58 96.90
18:50:01 11270.25 50853.00 431117.15 0.30 105697.26 3951.30
1951.31 5778.41 97.90
18:55:01 10086.69 59206.44 362027.12 0.70 104760.65 6928.91
1684.04 8497.73 98.66
Sluggish'ness starts at 18:10'ish and continues. Load drops and IO is very
small..
All good suggestions welcome.
sysctl changes
$ grep '^vm' /etc/sysctl.conf
vm.swappiness = 0
vm.dirty_background_ratio = 3
vm.dirty_ratio = 15
vm.dirty_expire_centisecs = 500
vm.dirty_writeback_centisecs = 100
Thanks
Jesper
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Subject: Re: Large memory machine and PG 9.2.9
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