Huge Page Support
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Huge Pages
- Huge pages are also known as superpages in FreeBSD, and large pages in Microsoft Windows terminology.
- Newer AMD64 processors can use 1GB pages in long mode.
- Linux has supported huge pages on several architectures since the 2.6 series via the hugetlbfs filesystem.
- Xen Project supports allocating huge pages for guest. The hypervisor itself doesn't use huge pages.
Using Huge Pages
- Specify the hypervisor boot command line flag `allowsuperpage` (it was called `allowhugepage` before).
- Create the VM with option `superpages = 1`.
Notes:
1. This option is for PV guest only; it has no effect to HVM guest. 2. With this option, PV guest `memory` and `maxmem` must be 2M aligned. Otherwise the VM cannot be started.
- Specify the Linux boot command line flag `balloon_hugepages`.
- In the guest::
# echo 20 > /proc/sys/vm/nr_hugepages # cat /proc/meminfo ... AnonHugePages: 0 kB HugePages_Total: 20 HugePages_Free: 20 HugePages_Rsvd: 0 HugePages_Surp: 0 Hugepagesize: 2048 kB DirectMap4k: 1056768 kB DirectMap2M: 0 kB