Re: Interpreting shared_buffers setting - Mailing list pgsql-performance

From Andrew Gierth
Subject Re: Interpreting shared_buffers setting
Date
Msg-id 87lg33haza.fsf@news-spur.riddles.org.uk
Whole thread Raw
In response to Interpreting shared_buffers setting  (Bob Jolliffe <bobjolliffe@gmail.com>)
Responses Re: Interpreting shared_buffers setting  (Bob Jolliffe <bobjolliffe@gmail.com>)
List pgsql-performance
>>>>> "Bob" == Bob Jolliffe <bobjolliffe@gmail.com> writes:

 Bob> Excuse me if this is a silly question. I am trying to fiddle with
 Bob> shared_buffers setting on postgresql 10.6 on ubuntu 18.04 server.

 Bob> I have this at bottom of my config file:
 Bob> shared_buffers = 1GB

 Bob> Yet when I check the setting from pg_setting I see something quite
 Bob> different:

 Bob> postgres=# SELECT name, setting FROM pg_settings where name = 'shared_buffers';
 Bob>       name      | setting
 Bob> ----------------+---------
 Bob>  shared_buffers | 131072

pg_settings can tell you more than you asked for:

postgres=# select * from pg_settings where name='shared_buffers';
-[ RECORD 1 ]---+-------------------------------------------------------------
name            | shared_buffers
setting         | 16384
unit            | 8kB
category        | Resource Usage / Memory
short_desc      | Sets the number of shared memory buffers used by the server.
extra_desc      | 
context         | postmaster
vartype         | integer
source          | configuration file
min_val         | 16
max_val         | 1073741823
enumvals        | 
boot_val        | 1024
reset_val       | 16384
sourcefile      | /home/andrew/work/pgsql/inst/9.5/data/postgresql.conf
sourceline      | 113
pending_restart | f

notice that "unit 8kB" line; the displayed integer value is in units of
8kB (which is the block size your server was compiled with, which you
can also see as the block_size parameter).

-- 
Andrew (irc:RhodiumToad)


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