Re: Reducing power consumption on idle servers

On Wed, 30 Nov 2022 at 03:50, Thomas Munro <thomas(dot)munro(at)gmail(dot)com> wrote:
>
> On Wed, Nov 30, 2022 at 1:32 AM Simon Riggs
> <simon(dot)riggs(at)enterprisedb(dot)com> wrote:
> > Re-attaching patch for bgwriter and walwriter, so it is clear this is
> > not yet committed.
>
> I'm just curious, and not suggesting that 60s wakeups are a problem
> for the polar ice caps, but why even time out at all? Are the latch
> protocols involved not reliable enough? At a guess from a quick
> glance, the walwriter's is but maybe the bgwriter could miss a wakeup
> as it races against StrategyGetBuffer(), which means you might stay
> asleep until the *next* buffer allocation, but that's already true I
> think, and a 60s timeout is not much of a defence.

That sounds reasonable.

It does sound like we agree that the existing behavior of waking up
every 5s or 2.5s is not good. I hope you will act to improve that.

The approach taken in this patch, and others of mine, has been to
offer a minimal change that achieves the objective of lengthy
hibernation to save power.

Removing the timeout entirely may not work in other circumstances I
have not explored. Doing that requires someone to check it actually
works, and for others to believe that check has occurred. For me, that
is too time consuming to actually happen in this dev cycle, and time
is part of the objective since perfect designs yet with unreleased
code have no utility.

<Simon enters lengthy hibernation>

--
Simon Riggs http://www.EnterpriseDB.com/