Re: Out of memory: postgres killed after changing "checkoint_completion_target" and reloading postgres configuration file

On 12/08/2014 12:47 PM, Pierre Slania wrote:
> Problem :
> ------------
> Dec  4 10:42:41 "myserver" kernel: [7604991.147522] Out of memory: Kill process 2904 (postgres) score 217 or
sacrificechild 
>
> How to cause the error:
> -----------------------------
> I changed the parameter "checkpoint_completion_target" from 0.5 to 0.9 in the postgresql.conf file unless the
productionis up and used by multiple users. After that I made a postgres reload the 4th dec 2014 at 10:20AM 
>
> (Note that same problem has occurred several weeks ago when I changed "checkpoint_segment" from 3 to 10 in the
postgresql.conffile after reloading postgres) 
>
> Application that are running
> -----------------------------------
> AS JBoss  7.1.1.Final with a connection pool
>
> Postgres version running in production
> ------------------------------------------------
> PostgreSQL 9.1.8 on x86_64-unknown-linux-gnu, compiled by gcc-4.4.real (Debian 4.4.5-8) 4.4.5, 64-bit
>
> OS Server production
> --------------------------
> Linux "myserver" 3.2.0-4-amd64 #1 SMP Debian 3.2.51-1 x86_64 GNU/Linux
>
> The following memories value was done today:
>
> postgres@"myserver":/var/log/postgresql$ free -m
>                       total        used         free        shared    buffers     cached
> Mem:         32115      29498       2617          0            110              20128
> -/+ buffers/cache:       9258      22857
> Swap:            0          0          0
>
> ð  No swap allowed in this server
>
> Observation:
> ----------------
> The database seems to run well from the 4th dec between 10:20AM to 10:42 AM before falling back suddently to out of
memory.
> It switched to recovery mode and restart automatically.
> There were no problem encountered like that before making any change to the checkpoint parameters.
>
> Attached files
> -----------------
> Syslog file and postgresql.log  file are attached. I made some clean up in the postgres log file.
>
> Question:
> ------------
> Is it not recommended to change any "checkpoint_xxx" parameters in the postgresql.conf file when the production is
running? 

There's no such recommendation. It should be totally fine to change
those parameters. I don't know why you got the OOM error, but I don't
see changing checkpoint settings could cause that.

- Heikki