Configuring HugePages for PostgreSQL

Memory is managed in block units called pages, and the default page size for x86 architecture is 4096 bytes. HugePages is a feature that manages memory with larger page sizes (2 MB by default), so the overview is that using huge pages reduces overhead when the shared_buffers value is large.

Pre-check

Verify that HugePages is supported by the kernel.

Build the Linux kernel with CONFIG_HUGETLBFS and CONFIG_HUGETLB_PAGE configuration options.

grep Huge /proc/meminfo

For PostgreSQL, estimate the number of hugepages according to the manual below. There is no script like Oracle’s hugepages_settings.sh.

18.4. Managing Kernel Resources https://www.postgresql.jp/document/10/html/kernel-resources.html#LINUX-HUGE-PAGES

How to Estimate the Required Number of HugePages

[postgres@postdb ~]$ head -1 $PGDATA/postmaster.pid
5811
[postgres@postdb ~]# grep ^VmPeak /proc/5811/status
VmPeak:	 5565496 kB
[postgres@postdb ~]# grep ^Hugepagesize /proc/meminfo
Hugepagesize:       2048 kB

From the above, 5565496kb/2048kb = 2,717.52734375, so we can determine that 2718 hugepages are needed.

OS-Side Configuration

sysctl -w vm.nr_hugepages=2718

Persist this value by setting it in /etc/sysctl.conf so it is used after a restart.

cat "vm.nr_hugepages=2718" >> /etc/sysctl.conf

Verifying HugePages Allocation

grep Huge /proc/meminfo

[postgres@postdb ~]$ grep Huge /proc/meminfo
AnonHugePages:         0 kB
ShmemHugePages:        0 kB
HugePages_Total:    2718
HugePages_Free:     2638
HugePages_Rsvd:     2511
HugePages_Surp:        0
Hugepagesize:       2048 kB
[postgres@postdb ~]$

Set Parameter on the DB Side (postgresql.conf)

huge_pages=on

Verify the parameter just to be sure:

[postgres@postdb data]$ psql
psql (10.11)
Type "help" for help.

postgres=#
postgres=# show huge_pages;
 huge_pages
------------
 on
(1 row)

Reference