From: Kevin Grittner <Kevin.Grittner@wicourts.gov>
To: Scott Marlowe <scott.marlowe@gmail.com>
To: Tom Lane <tgl@sss.pgh.pa.us>
Cc: Michael Monnerie <michael.monnerie@is.it-management.at>
Cc: pgsql-admin@postgresql.org
Subject: Re: Vacuum wait time problem
Date: Sun, 15 Feb 2009 12:50:01 -0600
Message-ID: <49980F79.EE98.0025.0@wicourts.gov> (raw)
In-Reply-To: <dcc563d10902131824n72051a44he60bc8d1d7467e5e@mail.gmail.com>
References: <4995ABC0.4090401@musicreports.com>
<200902140102.09224@zmi.at>
<dcc563d10902131708x2e8dfdadofc6355d8c27c6430@mail.gmail.com>
<23106.1234576963@sss.pgh.pa.us>
<dcc563d10902131824n72051a44he60bc8d1d7467e5e@mail.gmail.com>
>>> Scott Marlowe <scott.marlowe@gmail.com> wrote:
> On Fri, Feb 13, 2009 at 7:02 PM, Tom Lane <tgl@sss.pgh.pa.us> wrote:
>> Scott Marlowe <scott.marlowe@gmail.com> writes:
>>> On Fri, Feb 13, 2009 at 5:02 PM, Michael Monnerie
>>> <michael.monnerie@is.it-management.at> wrote:
>>>> vacuum_cost_delay = 0
>>>> That was the trick for me. It was set to 250(ms), where it took 5
>>>> hours for a vacuum to run. Now it takes 5-15 minutes.
>>
>>> Wow!!! 250 ms is HUGE in the scheme of vacuum cost delay. even
>>> 10ms is usually plenty to slow down vacuum enough to keep it out
>>> of your way and double to quadruple your vacuum times.
>>
>> I wonder whether we ought to tighten the allowed range of
>> vacuum_cost_delay. The upper limit is 1000ms at the moment;
>> but that's clearly much higher than is useful, and it seems
>> to encourage people to pick silly values ...
>
> I agree. I can't imagine using a number over 50 or so.
I don't know what other people have found useful, but when I
experimented with this in our environment, it seemed like I should
just treat vacuum_cost_delay as a boolean, where 0 meant off and 10
meant on, and tune it by adjusting vacuum_cost_limit. The granularity
of vacuum_cost_delay is course and surprising unpredictable.
-Kevin
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To: pgsql-admin@postgresql.org
Cc: Kevin.Grittner@wicourts.gov, scott.marlowe@gmail.com, tgl@sss.pgh.pa.us, michael.monnerie@is.it-management.at
Subject: Re: Vacuum wait time problem
In-Reply-To: <49980F79.EE98.0025.0@wicourts.gov>
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