Public bug reported:
In previous releases (tested with Saucy), if one wanted to use hugetlbfs
for a VM, the needed procedure was:
1) Add "vm.nr_hugepages" to /etc/sysctl.d/60-hugepages.conf
2) start procps
3) Set KVM_HUGEPAGES=1 in /etc/default/qemu-kvm
4) restart qemu-kvm
5) Enable "<memoryBacking> <hugepages/></memoryBacking>" in the libvirt guest
definition
6) Restart the guest
Now with Trusty, this doesn't work anymore as there is no (obvious?) way
to have the hugetlbfs mounted where QEMU expects it.
On Saucy, the upstart job for qemu-kvm contains this:
# mount hugepages if available and requested
if [ "$KVM_HUGEPAGES" -eq "1" ]; then
if ! grep -q hugetlbfs /proc/filesystems; then
logger -t qemu-kvm "Error: hugepages not available in
the kernel!"
elif grep -q /run/hugepages/kvm /proc/mounts; then
logger -t qemu-kvm "/run/hugepages/kvm already mounted"
elif ! grep -q kvm /etc/group; then
logger -t qemu-kvm "Error: group kvm does not exist!"
else
kvmgid=`grep kvm /etc/group | cut -d: -f 3`
mkdir -p /run/hugepages/kvm
mount -t hugetlbfs hugetlbfs-kvm -o
mode=775,gid=$kvmgid /run/hugepages/kvm
fi
fi
But it seems there is nothing similar in Trusty and manually mounting
the hugetlbfs doesn't help as qemu cannot find it there.
Host information:
$ lsb_release -rd
Description: Ubuntu 14.04 LTS
Release: 14.04
$ apt-cache policy qemu-system-x86 libvirt-bin
qemu-system-x86:
Installed: 2.0.0+dfsg-2ubuntu1
Candidate: 2.0.0+dfsg-2ubuntu1
Version table:
*** 2.0.0+dfsg-2ubuntu1 0
500 http://archive.ubuntu.com/ubuntu/ trusty-proposed/main amd64
Packages
100 /var/lib/dpkg/status
2.0.0~rc1+dfsg-0ubuntu3.1 0
500 http://archive.ubuntu.com/ubuntu/ trusty-updates/main amd64 Packages
500 http://security.ubuntu.com/ubuntu/ trusty-security/main amd64
Packages
2.0.0~rc1+dfsg-0ubuntu3 0
500 http://archive.ubuntu.com/ubuntu/ trusty/main amd64 Packages
libvirt-bin:
Installed: 1.2.2-0ubuntu13.1
Candidate: 1.2.2-0ubuntu13.1
Version table:
*** 1.2.2-0ubuntu13.1 0
500 http://archive.ubuntu.com/ubuntu/ trusty-updates/main amd64 Packages
100 /var/lib/dpkg/status
1.2.2-0ubuntu13 0
500 http://archive.ubuntu.com/ubuntu/ trusty/main amd64 Packages
ProblemType: Bug
DistroRelease: Ubuntu 14.04
Package: qemu-system-common 2.0.0+dfsg-2ubuntu1
ProcVersionSignature: Ubuntu 3.13.0-24.46-generic 3.13.9
Uname: Linux 3.13.0-24-generic x86_64
ApportVersion: 2.14.1-0ubuntu3
Architecture: amd64
CurrentDesktop: Unity
Date: Fri May 2 10:05:18 2014
InstallationDate: Installed on 2014-01-26 (95 days ago)
InstallationMedia: Ubuntu 14.04 LTS "Trusty Tahr" - Alpha amd64 (20140124)
SourcePackage: qemu
UpgradeStatus: No upgrade log present (probably fresh install)
** Affects: qemu (Ubuntu)
Importance: Undecided
Status: New
** Tags: amd64 apport-bug package-from-proposed trusty
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https://bugs.launchpad.net/bugs/1315402
Title:
No easy way to use hugetlbfs with QEMU
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