From: | Josh Trutwin <josh(at)trutwins(dot)homeip(dot)net> |
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To: | pgsql-performance(at)postgresql(dot)org |
Subject: | Re: Tuning Help - What did I do wrong? |
Date: | 2007-10-04 19:28:52 |
Message-ID: | 20071004142852.3cee0f42@joplin.trutwins.homeip.net |
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Lists: | pgsql-performance |
On Thu, 04 Oct 2007 14:03:07 -0500
"Kevin Grittner" <Kevin(dot)Grittner(at)wicourts(dot)gov> wrote:
> It's kind of silly to tell PostgreSQL that its total cache space is
> 10000 pages when you've got more than that in shared buffers plus
> all that OS cache space. Try something around 285000 pages for
> effective_cache_size.
Good point.
> > stats_command_string = on (was off)
> > stats_block_level = on (was off)
> > stats_row_level = on (was off)
>
> > After making these changes, the performance on the server actually
> > worsened. I slowly backed off on some of the paramaters but
> > didn't seem to help.
>
> Did you try turning off the collection of those additional
> statistics? That isn't free.
I turned off all but row level since I decided to try turning
autovacuum on.
> You didn't get specific about what you saw in performance
> problems. If you are seeing occasional "freezes" of all queries,
> you are likely looking at a known issue with "spikiness" of disk
> output. For some this can be corrected by using very aggressive
> background writer settings. Some have solved it by disabling OS
> write delays. Some haven't found a solution and are waiting for
> 8.3; there have been some serious changes made to attempt to
> resolve this issue.
Thanks - I put some additional information in replies to Scott, but
mainly the performance of the web sites that are talking to postgres
is the problem - people calling in, etc. I turned on slow query
logging to see if I can find if it's particular queries or something
else?
Josh
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