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From: Andrey Korolyov <andrey@xdel.ru>
Date: Thu, 1 Jun 2017 13:56:48 +0300
Message-ID: <CABYiri8vcRmOiH6ogGjXULuZXMo1Dh2a2nagLhSfUnS_B9+1Vg@mail.gmail.com>
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Subject: Re: [Qemu-devel] Tracking hugepages usage
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To: Vladyslav Drok <vdrok@mirantis.com>
Cc: "qemu-devel@nongnu.org" <qemu-devel@nongnu.org>

On Thu, Jun 1, 2017 at 1:38 PM, Vladyslav Drok <vdrok@mirantis.com> wrote:
> 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

Could you please try to walk against /proc/[0-9]/smaps to check that
these pages are not claimed by any process?