[Qemu-devel] Tracking hugepages usage

[Vladyslav Drok <vdrok@mirantis.com>]

Hello qemu community!

I come from openstack world, and one of our customers complains about an
issue with huge pages on compute nodes. From the "virsh frepages --all" and
"cat /proc/meminfo", they see that 4 huge pages are consumed:

http://paste.openstack.org/show/611186/

In total there are 239 1G pages, 120 in numa node 0, and 119 in numa node
1. There are no VMs running at this point.

When trying to find out what consumes the 4 1G huge pages from node 0, I
was suggesting "grep 1048576 /proc/*/numa_maps" to find out which processes
are using 1G pages, but in this particular case it shows no processes.
While when some VM is running, I can see the qemu process that's consuming
huge pages, numa_maps reports the correct amount of pages, corresponding to
what has been requested for the VM's RAM.

Are there any recommended ways for trying to track what consumes these 4
"lost" pages? (I might be a bit slow providing more info, as I don't have
access to this environment :( )

Thanks,
Vlad