KVM Huge Page Backed Memory
Enable KVM guests to use huge page backed memory in order to reduce memory consumption and improve performance by reducing CPU cache pressure.
- Targeted release: Fedora 12
- Last updated: 2009-09-24
- Percentage of completion: 100%
An SELinux issue in the kernel still remains, preventing full sVirt protection being applied to huge pages.
- KVM support for huge pages
- libvirt patch posted for running guests with
- libvirt patch-v2 posted which detects the host's hugetlbfs mount point automatically.
- Identify SELinux issue in the kernel
- Get the libvirt patch committed to libvirt-0.7.1
x86 CPUs usually address memory in 4kB pages, but they also have the ability to use huge pages (4MB on x86_32, 2MB on x86_64 and x86_32 PAE).
By using huge pages for a KVM guest's memory, less memory is used for page tables and TLB misses are reduced, thereby increasing performance.
Using huge pages for guest memory does have a downside, however - you can no longer swap nor balloon guest memory.
In order to use huge pages with KVM, one must do the following:
- Mount hugetlbfs to
mount -t hugetlbfs hugetlbfs /dev/hugepages
- Reserve some memory for huge pages -
- Pass the hugetlbfs path to
qemu-kvm -mem-path /dev/hugepages
This feature aims to improve allow huge pages to be used with libvirt managed guests.
Benefit to Fedora
Enables Fedora KVM hosts to achieve better performance.
- Test Plan
- Esperienza Utente
- Progetto corrente
- Note di rilascio
- Commenti e Discussioni
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