Re: Horrible CREATE DATABASE Performance in High Sierra

On 2017-10-02 15:54:43 -0400, Tom Lane wrote:
> Andres Freund <andres(at)anarazel(dot)de> writes:
> > On 2017-10-02 15:42:25 -0400, Tom Lane wrote:
> >> I experimented with this further by seeing whether the msync() code path
> >> is of any value on Sierra either. The answer seems to be "no": cloning
> >> a scale-1000 pgbench database takes about 17-18 seconds on my Sierra
> >> laptop using unmodified HEAD, but if I dike out the msync() logic then
> >> it takes 16-17 seconds. Both numbers jump around a little, but using
> >> msync is strictly worse.
>
> > Well, that's only measuring one type of workload. Could you run a normal
> > pgbench with -P1 or so for 2-3 checkpoint cycles and see how big the
> > latency differences are?
>
> Should I expect there to be any difference at all? We don't enable
> *_flush_after by default on non-Linux platforms.

Right, you'd have to enable that. But your patch would neuter an
intentionally enabled config too, no?

Greetings,

Andres Freund