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Re: Finding bottleneck

From: Gavin Sherry <swm(at)alcove(dot)com(dot)au>
To: Kari Lavikka <tuner(at)bdb(dot)fi>
Cc: pgsql-performance(at)postgresql(dot)org
Subject: Re: Finding bottleneck
Date: 2005-07-28 09:34:50
Message-ID: Pine.LNX.4.58.0507281931220.2769@linuxworld.com.au (view raw or flat)
Thread:
Lists: pgsql-performance
Hi,

On Thu, 28 Jul 2005, Kari Lavikka wrote:

> ----------------->8 Relevant rows from postgresql.conf 8<-----------------
>
> shared_buffers = 15000          # min 16, at least max_connections*2, 8KB each
> work_mem = 1536                 # min 64, size in KB

As an aside, I'd increase work_mem -- but it doesn't sound like that is
your problem.

> maintenance_work_mem = 32768    # min 1024, size in KB
>
> max_fsm_pages = 1000000         # min max_fsm_relations*16, 6 bytes each
> max_fsm_relations = 5000        # min 100, ~50 bytes each
>
> vacuum_cost_delay = 15          # 0-1000 milliseconds
> vacuum_cost_limit = 120         # 0-10000 credits
>
> bgwriter_percent = 2            # 0-100% of dirty buffers in each round
>
> fsync = true                    # turns forced synchronization on or off
>                                  # fsync, fdatasync, open_sync, or open_datasync
> wal_buffers = 128               # min 4, 8KB each

Some benchmarking results out today suggest that wal_buffers = 1024 or
even 2048 could greatly assist you.

> commit_delay = 80000            # range 0-100000, in microseconds
> commit_siblings = 10            # range 1-1000

This may explain the fact that you've got backed up queries and idle CPU
-- I'm not certain though. What does disabling commit_delay do to your
situation?

Gavin

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Subject: Re: Left joining against two empty tables makes a query SLOW
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Subject: Finding bottleneck

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