From: MichaelDBA <MichaelDBA@sqlexec.com>
To: Chris Hoover <chrish@aweber.com>
Cc: Ron <ronljohnsonjr@gmail.com>
Cc: pgsql-admin@lists.postgresql.org
Subject: Re: New PG14 server won't start with >2GB shared_buffers
Date: Sat, 25 Feb 2023 09:05:44 -0500
Message-ID: <4a41387e-516e-0782-6110-89c05a99d020@sqlexec.com> (raw)
In-Reply-To: <C6285AA6-5195-4C8B-A599-401845EFD174@aweber.com>
References: <A446608A-42A3-4CBB-BD45-47BE009B0029@aweber.com>
<4b583c4a-022f-f452-c0c8-0a932a6ee411@gmail.com>
<C6285AA6-5195-4C8B-A599-401845EFD174@aweber.com>
I just don't get what all this fuss is about trying to get PG up on the
smallest possible values for shared_buffers, especially considering this
person has 1 TB of memory?
Chris Hoover wrote on 2/25/2023 8:07 AM:
> Ron,
>
> Honestly, I grabbed 500MB to get the database up, by this time I was
> very frustrated and just wanted it up. :) I think I was at 1500MB
> and it still would not start. So to save what was left of my evening
> out, I just picked 500.
>
> Here is shmall:
> kernel.shmall = 17179869184
>
> Thanks,
>
>
> Chris Hoover
> Senior DBA
> AWeber.com
> Cell: (803) 528-2269
> Email: chrish@aweber.com
>
>
>
>> On Feb 25, 2023, at 5:25 AM, Ron <ronljohnsonjr@gmail.com> wrote:
>>
>> 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@aweber.com
>>>
>>>
>>>
>>
>> --
>> Born in Arizona, moved to Babylonia.
>
Regards,
Michael Vitale
Michaeldba@sqlexec.com <mailto:michaelvitale@sqlexec.com>
703-600-9343
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To: pgsql-admin@postgresql.org
Cc: MichaelDBA@sqlexec.com, chrish@aweber.com, ronljohnsonjr@gmail.com, pgsql-admin@lists.postgresql.org
Subject: Re: New PG14 server won't start with >2GB shared_buffers
In-Reply-To: <4a41387e-516e-0782-6110-89c05a99d020@sqlexec.com>
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