Thread: Interpreting shared_buffers setting
Excuse me if this is a silly question. I am trying to fiddle with
shared_buffers setting on postgresql 10.6 on ubuntu 18.04 server.
I have this at bottom of my config file:
shared_buffers = 1GB
Yet when I check the setting from pg_setting I see something quite different:
postgres=# SELECT name, setting FROM pg_settings where name = 'shared_buffers';
name | setting
----------------+---------
shared_buffers | 131072
Is this a question of units? It looks like 128M. Note when I change
the setting to 2GB in conf file I see 262144 from pg_setting. I am
now unsure what the actual shared_buffers allocation is. I cant see
anything in the docs which tells me how to interpret the integer.
Any clarification welcome.
Regards
Bob
Hi, check for blocksize (8k) as factor. 8k*131072=1G regards Thomas Am 29.01.19 um 13:32 schrieb Bob Jolliffe: > Excuse me if this is a silly question. I am trying to fiddle with > shared_buffers setting on postgresql 10.6 on ubuntu 18.04 server. > > I have this at bottom of my config file: > shared_buffers = 1GB > > Yet when I check the setting from pg_setting I see something quite different: > > postgres=# SELECT name, setting FROM pg_settings where name = 'shared_buffers'; > name | setting > ----------------+--------- > shared_buffers | 131072 > > Is this a question of units? It looks like 128M. Note when I change > the setting to 2GB in conf file I see 262144 from pg_setting. I am > now unsure what the actual shared_buffers allocation is. I cant see > anything in the docs which tells me how to interpret the integer. > > Any clarification welcome. > > Regards > Bob >
>>>>> "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)
Thank you Andrew and Thomas. All is now clear :-) On Tue, 29 Jan 2019 at 13:07, Andrew Gierth <andrew@tao11.riddles.org.uk> wrote: > > >>>>> "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)
Bob Jolliffe <bobjolliffe@gmail.com> writes:
> Excuse me if this is a silly question. I am trying to fiddle with
> shared_buffers setting on postgresql 10.6 on ubuntu 18.04 server.
>
> I have this at bottom of my config file:
> shared_buffers = 1GB
>
> Yet when I check the setting from pg_setting I see something quite different:
>
> postgres=# SELECT name, setting FROM pg_settings where name = 'shared_buffers';
> name | setting
> ----------------+---------
> shared_buffers | 131072
Why not use the show command which is good about output in human
terms...
psql (11.1 (Ubuntu 11.1-1.pgdg16.04+1))
Type "help" for help.
meta_a:postgres# select name, setting from pg_settings where name = 'shared_buffers');
ERROR: syntax error at or near ")"
LINE 1: ...me, setting from pg_settings where name = 'shared_buffers');
^
meta_a:postgres#
>
> Is this a question of units? It looks like 128M. Note when I change
> the setting to 2GB in conf file I see 262144 from pg_setting. I am
> now unsure what the actual shared_buffers allocation is. I cant see
> anything in the docs which tells me how to interpret the integer.
>
> Any clarification welcome.
>
> Regards
> Bob
>
>
--
Jerry Sievers
Postgres DBA/Development Consulting
e: postgres.consulting@comcast.net
Jerry Sievers <gsievers19@comcast.net> writes: > Bob Jolliffe <bobjolliffe@gmail.com> writes: > >> Excuse me if this is a silly question. I am trying to fiddle with >> shared_buffers setting on postgresql 10.6 on ubuntu 18.04 server. >> >> I have this at bottom of my config file: >> shared_buffers = 1GB >> >> Yet when I check the setting from pg_setting I see something quite different: >> >> postgres=# SELECT name, setting FROM pg_settings where name = 'shared_buffers'; >> name | setting >> ----------------+--------- >> shared_buffers | 131072 Aaaaay! Pasted junk... Here's what I meant. meta_a:postgres# select setting from pg_settings where name='shared_buffers'; setting --------- 131072 (1 row) meta_a:postgres# show shared_buffers; shared_buffers ---------------- 1GB (1 row) > > Why not use the show command which is good about output in human > terms... > > psql (11.1 (Ubuntu 11.1-1.pgdg16.04+1)) > Type "help" for help. > > meta_a:postgres# select name, setting from pg_settings where name = 'shared_buffers'); > ERROR: syntax error at or near ")" > LINE 1: ...me, setting from pg_settings where name = 'shared_buffers'); > ^ > meta_a:postgres# > >> >> Is this a question of units? It looks like 128M. Note when I change >> the setting to 2GB in conf file I see 262144 from pg_setting. I am >> now unsure what the actual shared_buffers allocation is. I cant see >> anything in the docs which tells me how to interpret the integer. >> >> Any clarification welcome. >> >> Regards >> Bob >> >> -- Jerry Sievers Postgres DBA/Development Consulting e: postgres.consulting@comcast.net