Re: Is there a significant difference in Memory settings between 9.5 and 12

On 5/11/20 1:42 PM, Tory M Blue wrote:
>
>
> On Mon, May 11, 2020 at 1:36 PM Tom Lane <tgl(at)sss(dot)pgh(dot)pa(dot)us
> <mailto:tgl(at)sss(dot)pgh(dot)pa(dot)us>> wrote:
>
> Tory M Blue <tmblue(at)gmail(dot)com <mailto:tmblue(at)gmail(dot)com>> writes:
> > 12 will not start at 10GB, even though it's the same hardware,
> same config
> > file, same physical box, same everything, just version 12 vs 9.5
>
> For me, using all-default settings (in particular, shared_buffers =
> 128MB), the shared memory block is about 141.6MB using 9.5 and 142.1MB
> using 12.  So there's half a meg or so of additional data in v12, but
> certainly not gigabytes worth.
>
> Are you trying to start both postmasters concurrently?  Maybe you're
> hitting some kernel limit on the total amount of shared memory in the
> system.
>
>                         regards, tom lane
>
>
> Hey Tom
>
> Nope, just a single one that is why i'm flummoxed :) I've even rebooted,
> but I can't start Postgres 12 with my current setting of 10GB, I can

So what is the error output from console, Postgres log and/or system log?

> start 9.5 with 10GB configured.   I've tried, shutting down 9.5 and
> rebooting so nothing is running and attempting to start 12 and nada, it
> won't unless I drop the Shared Buffers down to 5GB (half)..  But these
> are dedicated postgresql servers. And in fact my latest migrations,
> don't even have 9.5 binaries anymore and 12 will not start with my 9.5
> configuration of 10GB buffers. So something feels really different.
>
> It's very possible that there are new defaults , new memory settings
> that I'm not finding in the default postgresql 12 .conf file, and my
> include is not overwriting it. But really I just can't fathom what that
> could be.. Buffers, work mem, effective cache, what would they have added?
>
> I am going to pull the settings from postgres itself and compare 12 and
> 9.5 to see if there is something glaring.
>
> Thanks! :)
> Tory

--
Adrian Klaver
adrian(dot)klaver(at)aklaver(dot)com