Re: PGSQL 11.4: shared_buffers and /dev/shm size - Mailing list pgsql-general

From Konstantin Malanchev
Subject Re: PGSQL 11.4: shared_buffers and /dev/shm size
Date
Msg-id 63682227-874F-43A9-8879-DE875DE9BCC3@gmail.com
Whole thread Raw
In response to Re: PGSQL 11.4: shared_buffers and /dev/shm size  (Jean Louis <bugs@gnu.support>)
Responses Re: PGSQL 11.4: shared_buffers and /dev/shm size  (Jean Louis <bugs@gnu.support>)
List pgsql-general
Hello Jean,

I have 8 GB RAM and /dev/shm size is 4GB, and there is no significant memory usage by other system processes. I surprised that Postgres uses more space in /dev/shm than sharred_buffers parameter allows, probably I don't understand what this parameter means.

I have no opportunity to enlarge total RAM and probably this query requires too much RAM to execute. Should Postgres just use HDD as temporary storage in this case?


Konstantin

On 9 Jul 2019, at 12:53, Jean Louis <bugs@gnu.support> wrote:

* Konstantin Malanchev <hombit@gmail.com> [2019-07-09 11:51]:
Hello,

I'm running PostgreSQL 11.4 on Linux 4.12.14 and I see the following issue while executing single one query:
ERROR:  could not resize shared
memory segment "/PostgreSQL.1596105766" to 536870912 bytes: No space left on device

In my postgresql.conf I set sharred_buffers=256MB, I see that it is applied:
SHOW shared_buffers;
shared_buffers
----------------
256MB

At the same time during the query execution, I see a lot of files in /dev/shm with the total size more than 256MB

ls -lh /dev/shm

How can I configure limit for total shared memory size?

The limit is mostly set by the memory, as /dev/shm
is like virtual memory or RAM disk.

Increase the RAM.

Jean

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