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Re: Vacuum takes forever

From: Jim Nasby <decibel(at)decibel(dot)org>
To: Joost Kraaijeveld <J(dot)Kraaijeveld(at)Askesis(dot)nl>
Cc: postgresql performance list <pgsql-performance(at)postgresql(dot)org>
Subject: Re: Vacuum takes forever
Date: 2007-06-11 02:51:08
Message-ID: (view raw or whole thread)
Lists: pgsql-performance
On May 29, 2007, at 12:03 PM, Joost Kraaijeveld wrote:
> vacuum_cost_delay = 200
> vacuum_cost_page_hit = 6
> #vacuum_cost_page_miss = 10             # 0-10000 credits
> #vacuum_cost_page_dirty = 20            # 0-10000 credits
> vacuum_cost_limit = 100

I didn't see anyone else mention this, so...

Those settings are *very* aggressive. I'm not sure why you upped the  
cost of page_hit or dropped the cost_limit, but I can tell you the  
effect: vacuum will sleep at least every 17 pages... even if those  
pages were already in shared_buffers and vacuum didn't have to dirty  
them. I really can't think of any reason you'd want to do that.

I do find vacuum_cost_delay to be an extremely useful tool, but  
typically I'll set it to between 10 and 20 and leave the other  
parameters alone.
Jim Nasby                                            jim(at)nasby(dot)net
EnterpriseDB      512.569.9461 (cell)

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