From: | Jim Nasby <nasbyj(at)amazon(dot)com> |
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To: | Simon Riggs <simon(dot)riggs(at)enterprisedb(dot)com>, Andres Freund <andres(at)anarazel(dot)de>, Thomas Munro <thomas(dot)munro(at)gmail(dot)com> |
Cc: | PostgreSQL Hackers <pgsql-hackers(at)postgresql(dot)org> |
Subject: | Re: Reducing power consumption on idle servers |
Date: | 2022-03-03 22:41:42 |
Message-ID: | 09a03caf-b1eb-7634-ac41-5d3e55915847@amazon.com |
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Thread: | |
Lists: | pgsql-hackers |
On 2/21/22 10:11 AM, Simon Riggs wrote:
>>> * autovac launcher - autovacuum_naptime
>> On production systems autovacuum_naptime often can't be a large value,
>> otherwise it's easy to not keep up on small busy tables. That's fine for
>> actually busy servers, but with the increase in hosted PG offerings, the
>> defaults in those offerings needs to cater to a broader audience.
> Autovac varies its wakeup cycle according to how much work is done. It
> is OK to set autovacuum_naptime without affecting power consumption
> when idle.
I'm wondering how many people understand that. I've seen a number of
servers running very low values of autovacuum_naptime in order to make
things more responsive.
> Idle for autovac is defined slightly differently, since if all user
> work completes then there may still be a lot of vacuuming to do before
> it goes fully idle. But my observation is that there are many servers
> that go idle for more than 50% of each week, when operating 8-12 hours
> per day, 5 days per week, so we can still save a lot of power.
>
> This patch doesn't change how autovac works, it just uses a common
> setting for the hibernation that eventually occurs.
I'm wondering if it'd be worth linking autovac wakeup from a truly idle
state to the stats collector. If there's no stats messages coming in
clearly there's nothing new for autovac.
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