Huge-page support

Note: Across the IT industry, huge pages and large pages are used synonymously for memory pages that exceed 4 KB. In keeping with the more commonly used term in the context of Linux®, this publication uses huge pages.

Red Hat Enterprise Linux 9.2 LPAR mode z/VM guest KVM guest

Huge-page support entails support for the Linux hugetlbfs file system.

The huge-page support virtual file system is backed by larger memory pages than the usual 4 K pages; for IBM Z® the hardware page size is 1 MB.

To check whether 1 MB huge pages are supported in your environment, issue the command:

# grep -o "edat" /proc/cpuinfo 
edat

An output line that lists edat as a feature indicates 1 MB huge-page support.

Applications that use huge-page memory save a considerable amount of page table memory. Another benefit from the support might be an acceleration in the address translation and overall memory access speed.

As of version 7, Red Hat® Enterprise Linux also supports libhugetlbfs linking. For more information, see the libhugetlbfs package, libhugetlbfs-<version>.s390x.rpm, and the how-to document that is included in the package.

As of version 7, Red Hat Enterprise Linux supports transparent hugepages. For more information, see Documentation/vm/transhuge.txt in the Linux source tree.

As of zEC12, you can also configure 2 GB huge pages if Linux is running on an LPAR or as a KVM guest. There is no flag that indicates 2GB support; the support is always there as of zEC12.