Re: [HACKERS] Horrible CREATE DATABASE Performance in High Sierra

Andres Freund <andres@anarazel.de> writes:
> On 2017-10-02 18:33:17 -0400, Tom Lane wrote:
>> I'm kind of surprised that machine B doesn't show obvious tanking in this
>> test given that msync() makes it suck so badly at copying a database.
>> I wonder what is different from the kernel's standpoint ... maybe the
>> sheer number of different files mmap'd by a single process during the
>> copy?

> Yea, that's curious. I've really no clue about OSX, so pardon my
> question: With HEAD and CREATE DATABASE, is it IO blocked or kernel cpu
> blocked?

What I saw was that the backend process was consuming 100% of (one) CPU,
while the I/O transaction rate viewed by "iostat 1" started pretty low
--- under 10% of what the machine is capable of --- and dropped from
there as the copy proceeded.  I did not think to check if that was user
or kernel-space CPU, but I imagine it has to be the latter.
        regards, tom lane


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