CPU Load question / PgBouncer config

From: "Benjamin Krajmalnik" <kraj(at)servoyant(dot)com>
To: "pgsql-admin" <pgsql-admin(at)postgresql(dot)org>
Subject: CPU Load question / PgBouncer config
Date: 2012-05-14 17:02:30
Message-ID: F4E6A2751A2823418A21D4A160B68988A5D331@fletch.stackdump.local
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I am experiencing a little higher CPU load than I would like to see, and
was wondering if it has to do with the number of connections (although
many are idle).

I am running PG 9.0.4/amd64 on FreeBSD 8.1., dual boxes running
streaming replication.

Hardware is a 16 core box with 96GB RAM, using 6GB of shared buffers.

RAID 1 for OS, 12 drive RAID 10 for data, RAID 1 for logs.

I am using pgbouncer as a connection pooler, with 200 max client
connections, a default pool size of 100, and a reserve of 80.

The number of backends running are between 40 and 70. I monitor the
number of non-idle connections. Average is about 20, with non-frequent
spikes going to about 40.

My gut feeling is that I can probably reduce the pool size somewhat.

Would reducing the number of backends relieve some of the load on the
server (I am seeing a 5 min load of 12 more often than I would like to)?

Also, for this size setup, what would be the recommended values for the
pool sizes? I am certain the values are way above what they should be,
but nbot certain.

I posted here instead of the pgbouncer group hoping someone has
experienced similar things.

Prresently, I have the following load,

last pid: 96231; load averages: 12.18, 11.07, 10.97
up 112+19:23:29 11:02:05

and this is the result from checking the state of pgbouncer:

pgbouncer=# SHOW POOLS;

database | user | cl_active | cl_waiting | sv_active | sv_idle |
sv_used | sv_tested | sv_login | maxwait

-----------+-----------+-----------+------------+-----------+---------+-
--------+-----------+----------+---------

ishield | xxxxxxx | 48 | 0 | 48 | 4 |
2 | 0 | 0 | 0

pgbouncer | pgbouncer | 1 | 0 | 0 | 0 |
0 | 0 | 0 | 0

(2 rows)

pgbouncer=# SHOW POOLS;

database | user | cl_active | cl_waiting | sv_active | sv_idle |
sv_used | sv_tested | sv_login | maxwait

-----------+-----------+-----------+------------+-----------+---------+-
--------+-----------+----------+---------

ishield | xxxxxxx | 55 | 0 | 55 | 0 |
2 | 0 | 0 | 0

pgbouncer | pgbouncer | 1 | 0 | 0 | 0 |
0 | 0 | 0 | 0

(2 rows)

Thanks in advance,

Benjamin

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