Re: Multi processor server overloads occationally with system process while running postgresql-9.4 - Mailing list pgsql-performance

Sorry about the formatting.
I am posting the same lines again.

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/Linux Single database with separate tablespace
for main-data, pg_xlog and indexes

I 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.

sar command output

07:20:01  IST     CPU     %user     %nice   %system   %iowait    %steal
%idle
07:30:01  IST     all      0.73      0.00      0.37      0.58      0.00
98.33
07:40:01  IST     all      0.66      0.00      0.38      0.65      0.00
98.31
07:50:01  IST     all      0.27      0.00      0.27      0.01      0.00
99.45
08:00:01  IST     all      0.52      0.00      0.37      0.01      0.00
99.10
08:10:01  IST     all      1.54      0.00      0.70      0.02      0.00
97.74
08:20:01  IST     all      1.20      0.00      0.67      0.02      0.00
98.10
08:30:01  IST     all      1.48      0.00      0.77      0.03      0.00
97.72
08:40:01  IST     all      1.69      0.00      0.89      0.04      0.00
97.39
08:50:01  IST     all      1.71      0.00      0.94      0.04      0.00
97.31
09:00:01  IST     all      1.74      0.00      0.92      0.03      0.00
97.31
09:10:01  IST     all      2.32      0.00      1.06      0.04      0.00
96.58
09:20:01  IST     all      2.22      0.00      1.17      0.04      0.00
96.57
09:30:02  IST     all      2.20      0.00      6.68      0.06      0.00
91.06
09:40:01  IST     all      2.43      0.00      1.37      0.06      0.00
96.14
09:50:01  IST     all      3.23      0.00      2.06      0.08      0.00
94.63
10:00:02  IST     all      3.15      0.00      6.10      0.07      0.00
90.67
10:10:01  IST     all      4.94      0.00      5.20      0.29      0.00
89.57
10:20:01  IST     all      5.10      0.00      2.13      0.34      0.00
92.43
10:30:01  IST     all      5.60      0.00      2.42      0.18      0.00
91.80
10:40:01  IST     all      5.28      0.00     14.37      0.19      0.00
80.16
10:50:01  IST     all      4.52      0.00     28.48      0.23      0.00
66.77
11:00:01  IST     all      5.25      0.00      9.02      0.18      0.00
85.55
11:10:01  IST     all      5.77      0.00      4.96      0.27      0.00
89.00
11:20:01  IST     all      5.70      0.00      2.74      0.19      0.00
91.37
11:30:01  IST     all      5.72      0.00      5.91      0.20      0.00
88.17
11:40:01  IST     all      5.66      0.00      2.81      0.37      0.00
91.15
11:50:01  IST     all      5.90      0.00      8.80      0.10      0.00
85.19
12:00:01  IST     all      6.44      0.00      3.40      0.13      0.00
90.03
12:10:01  IST     all      7.18      0.00      4.52      0.11      0.00
88.18
12:20:02  IST     all      4.40      0.00     37.84      0.07      0.00
57.70
12:30:01  IST     all      5.66      0.00      2.98      0.10      0.00
91.26
12:40:01  IST     all      5.74      0.00      3.05      0.11      0.00
91.10
Average:        all      1.92      0.00      2.28      0.11      0.00
95.69


Postgresql.conf
max_connections = 500 (can be reduced)
shared_buffers = 8500MB work_mem = 50MB
maintenance_work_mem = 8064MB
checkpoint_segments = 132
checkpoint_timeout = 30min
checkpoint_completion_target = 0.9

I am not using a connection pooler.

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 help



Ajayakumar.BS



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