Re: Postgresql 14 performance - Mailing list pgsql-admin

On 8/22/22 09:17, Kenny Bachman wrote:

The huge_pages parameter is try. How can I know the huge page is used for shared buffers?

Also, I would like to say one more thing. Some queries have high planning time of explain analyze output. However, I run vacuumdb analyze command every day. I am a little bit confused about this.

Warm regards,

Kenn

Hi Kenny,

You can check by using grep -i huge /proc/meminfo. If your shared buffers are properly allocated, you will see something like this:

grep -i huge /proc/meminfo
AnonHugePages:         0 kB
ShmemHugePages:        0 kB
FileHugePages:         0 kB
HugePages_Total:    3072
HugePages_Free:        6
HugePages_Rsvd:        3
HugePages_Surp:        0
Hugepagesize:       2048 kB
Hugetlb:         6291456 kB

If, on the other side, huge pages are not allocated properly, you will get something like this:

grep -i huge /proc/meminfo
AnonHugePages:         0 kB
ShmemHugePages:        0 kB
FileHugePages:         0 kB
HugePages_Total:       0
HugePages_Free:        0
HugePages_Rsvd:        0
HugePages_Surp:        0
Hugepagesize:       2048 kB
Hugetlb:               0 kB

HugePages total and free will be equal. You need to put the right number into /etc/sysctl.conf:

grep vm.nr_hugepages /etc/sysctl.conf
vm.nr_hugepages=3072

Regards

-- 
Mladen Gogala
Database Consultant
Tel: (347) 321-1217
https://dbwhisperer.wordpress.com