[pgpool-general: 590] Re: load balancing seems to be bottlenecked by performance of master

Tatsuo Ishii ishii at postgresql.org
Tue Jun 5 08:25:33 JST 2012


> On Mon, Jun 4, 2012 at 3:40 PM, Tatsuo Ishii <ishii at postgresql.org> wrote:
>>> You're correct, I only needed to perform a reload.  I kept this change
>>> enabled for all of 36 seconds, and in that time there were 1597 times
>>> that the following query was logged originating from the pgpool server
>>> IP address:
>>> SELECT count(*) FROM pg_catalog.pg_class AS c WHERE c.oid ...
>>>
>>> 3204 times that the following query was logged originating from the
>>> pgpool server IP address:
>>> SELECT count(*) FROM pg_class AS c, pg_namespace AS n WHERE c.relname ...
>>>
>>> Those numbers seem excessive to me, but perhaps this is
>>> expected/normal?  It definitely seems like it would explain why perf
>>> always degrades whenever the master is very busy, if that volume of
>>> queries needs to be sustained.
>>
>> That depends on your use case. If client's query involves many tables,
>> it requires many catalog lookups. Also the catalog cache of pgpool's
>> life time is same as pgpool child process lifetime.  If you would show
>> me the complete log, I could make more precise analysis.
> 
> Sure, attached as pg.log.gz.

Thanks. This is helpfull. I will look into this.
--
Tatsuo Ishii
SRA OSS, Inc. Japan
English: http://www.sraoss.co.jp/index_en.php
Japanese: http://www.sraoss.co.jp


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