Re: High process memory consumption when running sort

On Wed, Mar 23, 2022 at 02:42:06PM +0000, Shai Shapira wrote:
> Hi,
>
> When running our application, we noticed that some processes are taking a lot of memory ( 10, 15, 20GB or so, of RSS ).
> It is also reproduced when running in psql.

Note that RSS can include shared_buffers read by that backend.
That's a linux behavior, not specific to postgres. It's what Andres was
describing here:
https://www.postgresql.org/message-id/flat/20201003230149(dot)mtd7fjsjwgii3jv7(at)alap3(dot)anarazel(dot)de

You have effective_cache_size = 48GB, so this seems to be working as intended.
(ecc is expected to include data cached not only by postgres but by the OS page
cache, too).

> Memory consumption: ( of case 2, application table, using system_stats )

I'm not sure, but I guess this is just a postgres view of whatever the OS
shows.

> Using top:
> PID USER PR NI VIRT RES SHR S %CPU %MEM TIME+ COMMAND
> 15298 postgres 20 0 16.8g 1.1g 1.1g S 0.0 1.7 0:02.63 postgres

> PostgreSQL 12.6 on x86_64-pc-linux-gnu, compiled by gcc (GCC) 4.8.5 20150623 (Red Hat 4.8.5-44), 64-bit
> Linux illin7504 3.10.0-1127.19.1.el7.x86_64 #1 SMP Tue Aug 11 19:12:04 EDT 2020 x86_64 x86_64 x86_64 GNU/Linux

> shared_buffers | configuration file | postmaster | 2097152 | 8kB | 1024
> effective_cache_size | configuration file | user | 6291456 | 8kB | 524288
> work_mem | configuration file | user | 20480 | kB | 4096