Rocky Linux Official 9 (9.5) AMI latest - difference in Total Memory

Rocky Linux Help & Support
1

We ran into an issue that seems to be related specifically to the updated Rocky Linux 9 AMI on AWS (on 27 Feb 2025).

We have narrowed it down to the initial Total Memory (on x3.xlarge instance).
It is lower than the 9.4 AMI and also lower than what we get on an Vsphere 9.5 instance.
from /proc/meminfo on a AWS 9.5 AMI:
MemTotal: 15903212 kB
MemFree: 15495492 kB
MemAvailable: 15458644 kB

AWS 9.4 AMI:
MemTotal: 16166432 kB
MemFree: 14679496 kB
MemAvailable: 15094804 kB

Vsphere 9.5 instance
MemTotal: 16113188 kB
MemFree: 15676824 kB
MemAvailable: 15610612 kB

These are all after an initial boot with either x3.xlarge AWS instance type or
16GB VM instance in Vsphere.

AMI ID: [ami-05150ea4d8a533099]
Also the official 9.5 AMI with LVM shows the same results.
At present, we cannot determine what is causing the difference in the AWS 9.5 AMI.

2

More research as determined that with the 9.5 release of the Rocky 9.5 AMI:
a crash kernel is configured which cause the reduction in available usable memory.

3

Edit /etc/kdump.conf and configure the line to match below by default it’s set to yes:

auto_reset_crashkernel no

then, do:

systemctl stop kdump
systemctl disable kdump
systemctl mask kdump

and then update Grub:

grub2-mkconfig --update-bls-cmdline -o /boot/grub2/grub.cfg

then you will reclaim the memory taken away by crashkernel. A reboot will be required.

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