[libvirt-users] HugePages - can't start guest that requires them

[G. Richard Bellamy]

Yeah, Dominique, your wiki was one of the many docs I read through
before/during/after starting down this primrose path... thanks for writing
it. I'm an Arch user, and I couldn't find anything to indicate qemu, as its
compiled for Arch, will look in /etc/default/qemu-kvm. And now that I've
got the right page size, the instances are starting...

The reason I want to use the page element to the hugepages directive is
that I want to target a numa node directly - in other words, I like the
idea of one VM running on Node 0, and the other running on Node 2.

Your comment about libvirt taking care of the hugepages mount isn't
consistent with my reading or experience - on a systemd-based system,
systemd takes care of the hugetlbfs mount to /dev/hugepages, and the
libvirt builds the /dev/hugepages/qemu... directory structure. At least
that's what I've seen.

-rb

On Sat, Jan 31, 2015 at 11:43 AM, Dominique Ramaekers <
dominique.ramaekers at cometal.be> wrote:

> Did you create a mount for the hugepages? If you did, that's maybe the
> problem. I did that also at first but with libvirt it isn't necessary and
> in my case, it broke hugepages...
>
> If I'm not mistaking, libvirt takes care of the hugepages mount.
>
> A while ago, I've written a wiki to use hugepages in libvirt and Ubuntu.
> https://help.ubuntu.com/community/KVM%20-%20Using%20Hugepages
>
> Maybe this helps?
>
> ________________________________________
> Van: G. Richard Bellamy [rbellamy at pteradigm.com]
> Verzonden: zaterdag 31 januari 2015 0:33
> Aan: libvirt-users at redhat.com
> Onderwerp: [libvirt-users] HugePages - can't start guest that requires them
>
> Hello All,
>
> I'm trying to enable hugepages, I've turned off THP (Transparent Huge
> Pages), and enabled hugepages in memoryBacking, and set my 2MB
> hugepages count via sysctl.
>
> I'm getting "libvirtd[5788]: Failed to autostart VM 'atlas': internal
> error: Unable to find any usable hugetlbfs mount for 16777216 KiB"
> where atlas is one of my guests and 16777216 KiB is the amount of
> memory I'm trying to give to the guest.
>
> Yes, i can see the hugepages via numastat -m and hugetlbfs is mounted
> via /dev/hugepages and there is a dir structure
> /dev/hugepages/libvirt/qemu (it's empty).
>
> HugePages is big enough to accommodate the 16G i'm allocating... and
> changing the perms on that directory structure to 777 doesn't work
> either.
>
> Any help is much appreciated.
>
> HOST: http://sprunge.us/SEdc
> GUEST: http://sprunge.us/VCYB
>
> Regards,
> Richard
>
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