Date: Mon, 25 Jul 2011 11:00:44 -0700 (PDT)
From: Filippos <filippos.kal@gmail.com>
To: pgsql-performance@postgresql.org
Message-ID: <1311616844194-4631760.post@n5.nabble.com>
Subject: heavy load-high cpu itilization
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Dear all

first of all congratulations on your greak work here since from time to time
i 've found many answers to my problems. unfortunately for this specific
problem i didnt find much relevant information, so i would ask for your
guidance dealing with the following situation:

we have a dedicated server (8.4.4, redhat) with 24 cpus and 36 GB or RAM. i
would say that the traffic in the server is huge and the cpu utilization is
pretty high too (avg ~ 75% except during the nights when is it much lower).
i am trying to tune the server a little bit to handle this problem. the
incoming data in the database are about 30-40 GB /day. 

at first the checkpoint_segments were set to 50, the checkpoint_timeout at
15 min and the checkpoint_completion_target was 0.5 sec.

i noticed that the utilization of the server was higher when it was close to
making a checkpoint and since the parameter of full_page_writes is ON , i
changed the parameters mentioned above to (i did that after reading a lot of
stuff online):
checkpoint_segments->250
checkpoint_timeout->40min
checkpoint_completion_target -> 0.8

but the cpu utilization is not significantly lower. another parameter i will
certainly change is the wal_buffers which is now set at 64KB and i plan to
make it 16MB. can this parameter cause a significant percentage of the
problem?

are there any suggestions what i can do to tune better the server? i can
provide any information you find relevant for the configuration of the
server, the OS, the storage etc

thank you in advance

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