Optimizing Linux Memory: When to Use Huge Pages and How to Disable THP

Huge Pages vs. Transparent Huge Pages

Linux supports two types of large memory pages: Huge Pages (standard large pages) and Transparent Huge Pages (THP) . Standard pages are pre‑allocated 2 MiB or 1 GiB blocks, while THP are created dynamically by the kernel.

Why Use Huge Pages?

Larger page size reduces the number of page table entries, improves TLB hit rates, lowers memory‑operation overhead, reduces kernel memory usage for page tables, eliminates swapping of those pages, and avoids kswapd activity.

Drawbacks and Compatibility

Enabling Huge Pages requires manual configuration and conflicts with Oracle 11g’s Automatic Memory Management (AMM), though Automatic Shared Memory Management (ASMM) still works. Transparent Huge Pages simplify usage but can cause instability in RAC clusters and performance issues on single‑node systems, especially for database workloads.

Disabling Transparent Huge Pages

Two methods are provided for CentOS 7.8:

Method 1 – Temporary Runtime Change

# echo never > /sys/kernel/mm/transparent_hugepage/enabled
# echo never > /sys/kernel/mm/transparent_hugepage/defrag

Setting the files to never disables THP until the next reboot.

Method 2 – Persistent GRUB Configuration

Backup the current GRUB configuration:

# cp /etc/default/grub /etc/default/grub.$(date +%F).bak
# cp /boot/grub2/grub.cfg /boot/grub2/grub.cfg.$(date +%F).bak

Edit /etc/default/grub (or /etc/sysconfig/grub) and append transparent_hugepage=never to GRUB_CMDLINE_LINUX:

GRUB_CMDLINE_LINUX="... transparent_hugepage=never"

Regenerate the GRUB configuration and reboot:

# grub2-mkconfig -o /boot/grub2/grub.cfg
# init 6

Verification

After reboot, confirm the settings:

# cat /sys/kernel/mm/transparent_hugepage/enabled
# cat /proc/meminfo | grep -i huge

The output should show [never] for the enabled file and zero values for AnonHugePages and HugePages_Total, indicating THP is disabled.

Monitoring THP Activity

Relevant runtime parameters can be inspected under /sys/kernel/mm/transparent_hugepage/, such as khugepaged/pages_to_scan, khugepaged/scan_sleep_millisecs, and khugepaged/alloc_sleep_millisecs, which control scanning frequency and defragmentation behavior.