Huge-page support

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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.

7.1 LPAR mode z/VM guest KVM guest

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

This virtual file system is backed by larger pages than the usual 4 KB 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 1MB 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 zEC12, you can also configure 2 GB huge pages if Linux is running on an LPAR or as a KVM guest.

The Linux kernel also supports transparent huge pages. For more information, see Documentation/vm/transhuge.txt in the Linux source tree.