Intermittent aggressive use of SWAP space by PostgreSQL despite availability of HUGE amounts of RAM for a small database.

We have been seeing intermittent aggressive use of SWAP space by PostgreSQL despite availability of HUGE amounts of free RAM. We have a 100 GB database with 256 GB RAM on the server so there is no shortage of RAM nor shortage in PostgreSQL buffer cache. Our swappiness setting is set to “1”.

What else can we do as far as PostgreSQL settings are concerned to make sure no/minimal swap is used. SWAP space is set at 8 GB. Is there a BUG related to this for which there has been a fix. Making changes to the application is too big of an effort which we cannot undertake at the moment.

Our PostgreSQL environment is as follows …

PostgreSQL 14.7 on x86_64-pc-linux-gnu, compiled by gcc (GCC) 8.5.0 20210514 (Red Hat 8.5.0-16), 64-bit

Red Hat environment details …

NAME="Red Hat Enterprise Linux"

VERSION="8.8 (Ootpa)"

ID="rhel"

ID_LIKE="fedora"

VERSION_ID="8.8"

PLATFORM_ID="platform:el8"

PRETTY_NAME="Red Hat Enterprise Linux 8.8 (Ootpa)"

ANSI_COLOR="0;31"

CPE_NAME="cpe:/o:redhat:enterprise_linux:8::baseos"

HOME_URL=https://www.redhat.com/

DOCUMENTATION_URL=https://access.redhat.com/documentation/en-us/red_hat_enterprise_linux/8

BUG_REPORT_URL=https://bugzilla.redhat.com/

REDHAT_BUGZILLA_PRODUCT="Red Hat Enterprise Linux 8"

REDHAT_BUGZILLA_PRODUCT_VERSION=8.8

REDHAT_SUPPORT_PRODUCT="Red Hat Enterprise Linux"

REDHAT_SUPPORT_PRODUCT_VERSION="8.8"

Hardware details …

[root@newdb ~]# lshw -short

H/W path             Device       Class          Description

============================================================

                                  system         PowerEdge R750 (SKU=090E;ModelName=PowerEdge R750)

/0                                bus            01J4WF

/0/1                              memory         64KiB BIOS

/0/400                            processor      Intel(R) Xeon(R) Gold 6346 CPU @ 3.10GHz

/0/400/700                        memory         1280KiB L1 cache

/0/400/701                        memory         20MiB L2 cache

/0/400/702                        memory         36MiB L3 cache

/0/401                            processor      Intel(R) Xeon(R) Gold 6346 CPU @ 3.10GHz

/0/401/703                        memory         1280KiB L1 cache

/0/401/704                        memory         20MiB L2 cache

/0/401/705                        memory         36MiB L3 cache

/0/1000                           memory         256GiB System Memory

/0/1000/0                         memory         32GiB DIMM DDR4 Synchronous Registered (Buffered) 3200 MHz (0.3 ns)

/0/1000/1                         memory         32GiB DIMM DDR4 Synchronous Registered (Buffered) 3200 MHz (0.3 ns)

/0/1000/2                         memory         32GiB DIMM DDR4 Synchronous Registered (Buffered) 3200 MHz (0.3 ns)

/0/1000/3                         memory         32GiB DIMM DDR4 Synchronous Registered (Buffered) 3200 MHz (0.3 ns)