Re: New PG14 server won't start with >2GB shared_buffers

Why did you have to drop shared buffers to 500MB, instead of something just
below 2GB?

And what's "your kernel's SHMALL parameter"?

On 2/24/23 20:08, Chris Hoover wrote:
> Hello All,
>
> Have a strange issue that I can not solve.
>
> I have a new server that has 1TB ram (not a typo).  I have been fighting
> with this evening to start up with a shared_buffer setting over 2GB.  When
> the memory allocation  breaks 2GB, the database won’t start.  I’ve dropped
> it down to 500M to get the database online.  We’ve tried both SysV memory
> and mmap memory.
>
> Any ideas on what is going on and how to resolve?  I’m sure I’m missing
> something obvious, but it is totally eluding me.
>
> OS: Ubuntu 18.04
> Memory:  1007GB
> CPU: Intel(R) Xeon(R) CPU           X7550  @ 2.00GHz (64 cores total)
>
> Kernel Memory:
> kernel.shmmax = 274877906944
> kernel.shmall = 17179869184
>
> Postgres Config:
>                   name                                  |              
>  setting
>  autovacuum_max_workers                 | 3
>  autovacuum_work_mem                     | -1
>  effective_cache_size                           | 98992128
>  fsync                                                    | on
>  full_page_writes                                  | on
>  maintenance_work_mem                    | 2097152
>  shared_buffers                                    | 64000
>  shared_memory_type                         | sysv
>  temp_buffers                                       | 4096
>  wal_buffers                                         | 2048
>  work_mem                                          | 119990
>
> If you need additional parameters, please ask
>
> SysV Error:
> Feb 25 01:55:16 appdb-server01.production.aweberint.com postgres[34680]:
> FATAL:  could not create shared memory segment: Cannot allocate memory
> DETAIL:  Failed system call was shmget(key=2359323, size=2063564800, 03600).
> HINT:  This error usually means that PostgreSQL's request for a shared
> memory segment exceeded your kernel's SHMALL parameter.  You might need to
> reconfigure the kernel with larger SHMALL.
>
> Mmap Error:
> FATAL:  could not map anonymous shared memory: Cannot allocate memory
> HINT:  This error usually means that PostgreSQL's request for a shared
> memory segment exceeded available memory, swap space, or huge pages. To
> reduce the request size (currently 1635737600 bytes), reduce PostgreSQL's
> shared memory usage, perhaps by reducing shared_buffers or max_connections.
>
> Thanks,
>
>
> Chris Hoover
> Senior DBA
> AWeber.com
> Cell: (803) 528-2269
> Email: chrish(at)aweber(dot)com
>
>
>

--
Born in Arizona, moved to Babylonia.