From: Mina Almasry <almasrymina@google.com>
To: David Hildenbrand <david@redhat.com>
Cc: "linux-kernel@vger.kernel.org" <linux-kernel@vger.kernel.org>,
"linux-mm@kvack.org" <linux-mm@kvack.org>,
Michal Privoznik <mprivozn@redhat.com>,
"Michael S. Tsirkin" <mst@redhat.com>,
Michal Hocko <mhocko@kernel.org>,
Muchun Song <songmuchun@bytedance.com>,
"Aneesh Kumar K.V" <aneesh.kumar@linux.vnet.ibm.com>,
Tejun Heo <tj@kernel.org>
Subject: Re: cgroup and FALLOC_FL_PUNCH_HOLE: WARNING: CPU: 13 PID: 2438 at mm/page_counter.c:57 page_counter_uncharge+0x4b/0x5
Date: Wed, 14 Oct 2020 10:56:46 -0700 [thread overview]
Message-ID: <CAHS8izPEHZunoeXYS5ONfRoSRMpC7DQwtpjJ8g4nXiddTfNoaA@mail.gmail.com> (raw)
In-Reply-To: <563d1eef-b780-835a-ebf0-88ae111b20c2@redhat.com>
On Wed, Oct 14, 2020 at 9:15 AM David Hildenbrand <david@redhat.com> wrote:
>
> On 14.10.20 17:22, David Hildenbrand wrote:
> > Hi everybody,
> >
> > Michal Privoznik played with "free page reporting" in QEMU/virtio-balloon
> > with hugetlbfs and reported that this results in [1]
> >
> > 1. WARNING: CPU: 13 PID: 2438 at mm/page_counter.c:57 page_counter_uncharge+0x4b/0x5
> >
> > 2. Any hugetlbfs allocations failing. (I assume because some accounting is wrong)
> >
> >
> > QEMU with free page hinting uses fallocate(FALLOC_FL_PUNCH_HOLE)
> > to discard pages that are reported as free by a VM. The reporting
> > granularity is in pageblock granularity. So when the guest reports
> > 2M chunks, we fallocate(FALLOC_FL_PUNCH_HOLE) one huge page in QEMU.
> >
> > I was also able to reproduce (also with virtio-mem, which similarly
> > uses fallocate(FALLOC_FL_PUNCH_HOLE)) on latest v5.9
> > (and on v5.7.X from F32).
> >
> > Looks like something with fallocate(FALLOC_FL_PUNCH_HOLE) accounting
> > is broken with cgroups. I did *not* try without cgroups yet.
> >
> > Any ideas?
Hi David,
I may be able to dig in and take a look. How do I reproduce this
though? I just fallocate(FALLOC_FL_PUNCH_HOLE) one 2MB page in a
hugetlb region?
>
> Just tried without the hugetlb controller, seems to work just fine.
>
> I'd like to note that
> - The controller was not activated
> - I had to compile the hugetlb controller out to make it work.
>
> --
> Thanks,
>
> David / dhildenb
>
next prev parent reply other threads:[~2020-10-14 17:57 UTC|newest]
Thread overview: 18+ messages / expand[flat|nested] mbox.gz Atom feed top
2020-10-14 15:22 cgroup and FALLOC_FL_PUNCH_HOLE: WARNING: CPU: 13 PID: 2438 at mm/page_counter.c:57 page_counter_uncharge+0x4b/0x5 David Hildenbrand
2020-10-14 16:15 ` David Hildenbrand
2020-10-14 17:56 ` Mina Almasry [this message]
2020-10-14 18:18 ` David Hildenbrand
2020-10-14 18:31 ` Mike Kravetz
2020-10-15 7:56 ` David Hildenbrand
2020-10-15 8:57 ` David Hildenbrand
2020-10-15 9:01 ` David Hildenbrand
2020-10-15 23:14 ` Mike Kravetz
2020-10-20 13:38 ` David Hildenbrand
2020-10-21 3:35 ` Mike Kravetz
2020-10-21 12:42 ` David Hildenbrand
2020-10-21 12:57 ` Michal Privoznik
2020-10-21 13:11 ` David Hildenbrand
2020-10-21 13:34 ` David Hildenbrand
2020-10-21 13:38 ` David Hildenbrand
2020-10-21 16:58 ` Mike Kravetz
2020-10-21 17:30 ` David Hildenbrand
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