Re: Excessive PostmasterIsAlive calls slow down WAL redo

On Tue, Apr 24, 2018 at 7:37 PM, Michael Paquier <michael(at)paquier(dot)xyz> wrote:
> I have been looking at the proposed set for Linux, and the numbers are
> here. By replaying 1GB worth of WAL after a pgbench run with the data
> folder on a tmpfs the recovery time goes from 33s to 28s, so that's a
> nice gain.

Thanks for testing.

> Do you have numbers with FreeBSD? I get that this would be more
> difficult to set up without a GA release perhaps...

I don't have production build numbers, but a similar test to yours
went from 91s to 61s on a debug kernel in a virtual machine.

> I can also see the difference in profiles by looking for
> HandleStartupProcInterrupts which gets close 10% of the attention when
> unpatched, and down to 0.1% when patched.
>
> @@ -2484,6 +2484,8 @@ ClosePostmasterPorts(bool am_syslogger)
> if (bonjour_sdref)
> close(DNSServiceRefSockFD(bonjour_sdref));
> #endif
> +
> + PostmasterDeathInit();
>
> Thomas, trying to understand here... Why this place for the signal
> initialization? Wouldn't InitPostmasterChild() be a more logical place
> as we'd want to have this logic caught by all other processes?

Yeah, you're right. Here's one like that.

--
Thomas Munro
http://www.enterprisedb.com