Change page size on CentOS

Follow the steps below to install a 64K page size kernel on CentOS 9 or later .

Verify the current page size

Verify you’re using a 4KB pagesize kernel by entering the following commands:

    

        
        
getconf PAGESIZE
uname -r

    

The output should be similar to below. The kernel flavor (the string after the version number) may vary, but the first line should always be 4096.

    

        
        4096
6.1.0-34-cloud-arm64

        
    

The 4096 indicates the current page size is 4KB. If you see a value that is different, you are already using a page size other than 4096 (4K). On Arm systems, the valid options are 4K, 16K, and 64K.

Install the 64K kernel package:

Enter the command below to install the 64K kernel:

    

        
        
sudo dnf -y install kernel-64k

    

You should see a page of output ending with:

    

        
        ...
Installed:
  kernel-64k-5.14.0-583.el9.aarch64                          kernel-64k-core-5.14.0-583.el9.aarch64                         
  kernel-64k-modules-5.14.0-583.el9.aarch64                  kernel-64k-modules-core-5.14.0-583.el9.aarch64                 

Complete!

        
    

Enter the following to configure the 64K kernel as default and reboot:

    

        
        
k=$(echo /boot/vmlinuz*64k)
sudo grubby --set-default "$k" --update-kernel "$k"
sudo reboot

    

Verify the page size and kernel version:

Upon reboot, check the kernel page size and name once again to confirm the changes:

    

        
        
getconf PAGESIZE
uname -r

    

The output shows the 64k kernel is running:

    

        
        65536
5.14.0-583.el9.aarch64+64k

        
    

Revert to the 4K kernel

To revert to the original 4K kernel, enter the following:

    

        
        
# Get your running kernel (should be something like "5.14.0-583.el9.aarch64+64k")
curr=$(uname -r)

# Strip the "+64k" suffix
base=${curr%+64k}

# Build the full path to the 4K kernel image
k4="/boot/vmlinuz-${base}"

# Sanity‐check that it actually exists
if [[ ! -e "$k4" ]]; then
  echo "Cannot find 4K kernel image at $k4"
  exit 1
fi

echo "Found 4K kernel: $k4"

# remove any crashkernel args
sudo grubby --remove-args="crashkernel=2G-:640M" --update-kernel "$k4"

# set it as the default
sudo grubby --set-default "$k4"

# Reboot the system
sudo reboot

    

Upon reboot, verify you’re on a 4KB pagesize kernel by entering the following commands:

    

        
        
getconf PAGESIZE
uname -r

    

The output shows the 4k kernel is running:

    

        
        4096
6.1.0-34-cloud-arm64

        
    

The 4096 indicates the current page size has been reverted to 4KB.