/proc/meminfo:Shmem same on containers and host

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Alexis Huxley

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Jan 4, 2022, 7:17:03 AMJan 4
to lxc-users
Hi, inside an LXC container, /proc/meminfo:MemTotal corresponds with the container-specific restrictions, but /proc/meminfo:Shmem is the value from the host that the container runs on.

Is this a bug or is it meant to be like this?

The reason I ask is that CheckMK monitors the ratio between the two values and triggers an alert when a threshhold value is exceeded. On the host ('fiori' in the output below) and on containers that genuinely need a lot of  memory then the ratio is always well below the threshold. But on one container ('mandala' in the output), which needs only a little memory, the ratio is high enough to trigger alerts.

I understand that I can modify the CheckMK's threshold for this host, but before I do that I want to know whether (a) I should do thar or whether (b) I should submit an LXC bug report or whether (c) it's a fixed bug that just hasn't reached the distro I use (though googling didn't show that).

Any advice please?

In case it helps: this is Debian 11 running stock LXC (4.0.6) and stock lxcfs (4.0.7).

Alexis

farfalle# for HOST in fiori orzo armonie gnocchi paccheri mandala rotelle bigoli; do echo "=== $HOST ==="; echo; ssh -n $HOST "egrep '^(Shmem|MemTotal):' /proc/meminfo"; echo; done
=== fiori ===

MemTotal:       32121356 kB
Shmem:            240100 kB

=== orzo ===

MemTotal:        2097152 kB
Shmem:            240100 kB

=== armonie ===

MemTotal:        2097152 kB
Shmem:            240100 kB

=== gnocchi ===

MemTotal:        2097152 kB
Shmem:            240100 kB

=== paccheri ===

MemTotal:        2097152 kB
Shmem:            240100 kB

=== mandala ===

MemTotal:        1048576 kB
Shmem:            240100 kB

=== rotelle ===

MemTotal:        4194304 kB
Shmem:            240100 kB

=== bigoli ===

MemTotal:        2097152 kB
Shmem:            240100 kB

farfalle#

--

Serge E. Hallyn

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Feb 5, 2022, 10:09:52 PMFeb 5
to Alexis Huxley, lxc-users
On Tue, Jan 04, 2022 at 04:17:02AM -0800, Alexis Huxley wrote:
> Hi, inside an LXC container, /proc/meminfo:MemTotal corresponds with the
> container-specific restrictions, but /proc/meminfo:Shmem is the value from
> the host that the container runs on.
>
> Is this a bug or is it meant to be like this?
>
> The reason I ask is that CheckMK monitors the ratio between the two values
> and triggers an alert when a threshhold value is exceeded. On the host
> ('fiori' in the output below) and on containers that genuinely need a lot
> of memory then the ratio is always well below the threshold. But on one
> container ('mandala' in the output), which needs only a little memory, the
> ratio is high enough to trigger alerts.
>
> I understand that I can modify the CheckMK's threshold for this host, but
> before I do that I want to know whether (a) I should do thar or whether (b)
> I should submit an LXC bug report or whether (c) it's a fixed bug that just
> hasn't reached the distro I use (though googling didn't show that).
>
> Any advice please?

Did anyone ever answer this, in another forum?

From what I can see, the shmem reported by lxcfs should be the one which
came from cgroups, so it should not be the system-wide value.

> In case it helps: this is Debian 11 running stock LXC (4.0.6) and stock
> lxcfs (4.0.7).
>
> Alexis
>
> farfalle# *for HOST in fiori orzo armonie gnocchi paccheri mandala rotelle
> bigoli; do echo "=== $HOST ==="; echo; ssh -n $HOST "egrep
> '^(Shmem|MemTotal):' /proc/meminfo"; echo; done*
> --
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