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Re: PostgreSQL 8.4 performance tuning questions

From: tv(at)fuzzy(dot)cz
To: "Rauan Maemirov" <rauan(at)maemirov(dot)com>
Cc: pgsql-performance(at)postgresql(dot)org
Subject: Re: PostgreSQL 8.4 performance tuning questions
Date: 2009-07-30 13:39:42
Message-ID: (view raw, whole thread or download thread mbox)
Lists: pgsql-performance
> Hi, list. I've just upgraded pgsql from 8.3 to 8.4. I've used pgtune
> before and everything worked fine for me.
> And now i have ~93% cpu load. Here's changed values of config:
> default_statistics_target = 50
> maintenance_work_mem = 1GB
> constraint_exclusion = on
> checkpoint_completion_target = 0.9
> effective_cache_size = 22GB
> work_mem = 192MB
> wal_buffers = 8MB
> checkpoint_segments = 16
> shared_buffers = 7680MB
> max_connections = 80
> My box is Nehalem 2xQuad 2.8 with RAM 32Gb, and there's only
> postgresql working on it.
> For connection pooling i'm using pgbouncer's latest version with
> pool_size 20 (used 30 before, but now lowered) and 10k connections.
> What parameters i should give more attention on?

All the values seem quite reasonable to me. What about the _cost variables?

I guess one or more queries are evaluated using a different execution
plan, probably sequential scan instead of index scan, hash join instead of
merge join, or something like that.

Try to log the "slow" statements - see "log_min_statement_duration". That
might give you slow queries (although not necessarily the ones causing
problems), and you can analyze them.

What is the general I/O activity? Is there a lot of data read/written to
the disks, is there a lot of I/O wait?


PS: Was the database analyzed recently?

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Subject: Re: PostgreSQL 8.4 performance tuning questions
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