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

On 5/11/20 1:42 PM, Tory M Blue wrote:
> 
> 
> On Mon, May 11, 2020 at 1:36 PM Tom Lane <tgl@sss.pgh.pa.us 
> <mailto:tgl@sss.pgh.pa.us>> wrote:
> 
>     Tory M Blue <tmblue@gmail.com <mailto:tmblue@gmail.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.klaver@aklaver.com