the detail result is :
in the RHEL 8.X, PostgreSQL can use non-default hugepagesize， and in the RHEL 7.X, PostgreSQL can not use non-default hugepagesize！
[pg142@rhel85 data]$ cat /etc/redhat-release
Red Hat Enterprise Linux release 8.5 (Ootpa)
[pg142@rhel85 data]$ uname -r
4.18.0-348.el8.x86_64
[pg142@rhel85 data]$
[pg142@rhel85 ~]$ grep ^Huge /proc/meminfo
HugePages_Total: 0
HugePages_Free: 0
HugePages_Rsvd: 0
HugePages_Surp: 0
Hugepagesize: 1048576 kB ----->>> OS default hugepagesize is 1GB
Hugetlb: 0 kB
[pg142@rhel85 ~]$
[pg142@rhel85 ~]$ head -1 $PGDATA/postmaster.pid
1679
[pg142@rhel85 ~]$ pmap 1679| awk '/rw-s/ && /zero/ {print $2}'
828480K
[pg142@rhel85 ~]$
(828480K+256*1024)/2048=533 ----->>>PostgreSQL uses 533 hugepages which size is 2MB
in the /boot/grub2/grubenv file ，add: hugepagesz=2M hugepages=533
[root@rhel85 ~]# grub2-editenv - list | grep kernelopts
kernelopts=root=/dev/mapper/rhel-root ro crashkernel=auto resume=/dev/mapper/rhel-swap rd.lvm.lv=rhel/root rd.lvm.lv=rhel/swap rhgb quiet default_hugepagesz=1G
[root@rhel85 ~]#
grub2-editenv - set "kernelopts=root=/dev/mapper/rhel-root ro crashkernel=auto resume=/dev/mapper/rhel-swap rd.lvm.lv=rhel/root rd.lvm.lv=rhel/swap rhgb quiet default_hugepagesz=1G hugepagesz=2M hugepages=533"
grub2-editenv - list | grep kernelopts
systemctl reboot
after OS reboot, we can see :
root@rhel85 ~]# hugeadm --pool-list
Size Minimum Current Maximum Default
2097152 533 533 533
1073741824 0 0 0 *
[root@rhel85 ~]#
[root@rhel85 ~]# cat /proc/meminfo |grep -i huge
AnonHugePages: 16384 kB
ShmemHugePages: 0 kB
FileHugePages: 0 kB
HugePages_Total: 0
HugePages_Free: 0
HugePages_Rsvd: 0
HugePages_Surp: 0
Hugepagesize: 1048576 kB
Hugetlb: 1091584 kB
[root@rhel85 ~]#
then modify parameter huge_page_size=2048 in the postgreSQL 14.2 postgresql.conf
[pg142@rhel85 data]$ grep huge_page_size postgresql.conf
huge_page_size = 2048 # zero for system default
[pg142@rhel85 data]$
[pg142@rhel85 data]$ pg_ctl start
waiting for server to start....2022-05-13 21:26:24.051 CST [1694] LOG: starting PostgreSQL 14.2 on x86_64-pc-linux-gnu, compiled by gcc (GCC) 8.5.0 20210514 (Red Hat 8.5.0-3), 64-bit
2022-05-13 21:26:24.051 CST [1694] LOG: listening on IPv6 address "::1", port 5432
2022-05-13 21:26:24.051 CST [1694] LOG: listening on IPv4 address "127.0.0.1", port 5432
2022-05-13 21:26:24.053 CST [1694] LOG: listening on Unix socket "/tmp/.s.PGSQL.5432"
2022-05-13 21:26:24.058 CST [1695] LOG: database system was shut down at 2022-05-13 21:22:22 CST
2022-05-13 21:26:24.063 CST [1694] LOG: database system is ready to accept connections
done
server started
[pg142@rhel85 data]$ pg_ctl status
pg_ctl: server is running (PID: 1694)
/home/pg142/soft/bin/postgres
[pg142@rhel85 data]$
[pg142@rhel85 data]$ psql -d postgres
psql (14.2)
Type "help" for help.
postgres=# show huge_page_size;
huge_page_size
----------------
2MB
(1 row)
postgres=# show huge_pages;
huge_pages
------------
try
(1 row)
postgres=#
At 2022-05-10 00:58:31, "yanliang lei" <msdnchina@xxxxxxx> wrote:
Thanks a lot for your reply！Oh,I see！I will test this case in the rhel8.5（ RHEL 8.5 is the latest version of RHEL so far）I will post my test result through this email。
At 2022-05-10 00:27:14, "Tom Lane" <tgl@xxxxxxxxxxxxx> wrote: >"yanliang lei" <msdnchina@xxxxxxx> writes: >> The DETAIL message says " huge_page_size must be 0", but you did not set huge_page_size to 0. >> ---huge_page_size is the pg14 new parameter£¬The default value of this parameter is zero (0). When set to 0, the default huge page size on the system will be used. >> in the pg 14 documents---¡®Non-default settings are currently supported only on Linux.¡¯ so £¬ I want to try to find a method to let PostgreSQL 14 to use non-default hugepagesize£¬ > >The code that's throwing the error says > > /* Recent enough Linux only, for now. See GetHugePageSize(). */ > >I don't know what "recent enough" is in this context, but evidently >RHEL7 isn't it (no surprise considering that's a trailing-edge distro >at this point). > >I don't find it surprising that the authors of this feature didn't >try to document exactly which Linux versions it can be used on. >Keeping such documentation accurate would be a nightmare. > > regards, tom lane >
