/proc/swaps is incorrect in LXC (Bug?)

denos

Active Member
Jul 27, 2015
82
39
38
We've noticed that in recent versions of Proxmox, that /proc/swaps is wrong. It boils down to this inside the container:

Code:
# free -m
              total        used        free      shared  buff/cache   available
Mem:          64738         118       64610           7           8       64619
Swap:         16384           0       16384

That is correctly reporting 16384 free. Here's /proc/meminfo on the same container which is also correct:
Code:
# cat /proc/meminfo
MemTotal:       66291712 kB
MemFree:        66161292 kB
MemAvailable:   66170268 kB
Buffers:               0 kB
Cached:             8976 kB
SwapCached:            0 kB
Active:           100056 kB
Inactive:           8976 kB
Active(anon):     100056 kB
Inactive(anon):     8184 kB
Active(file):          0 kB
Inactive(file):      792 kB
Unevictable:           0 kB
Mlocked:           21992 kB
SwapTotal:      16777216 kB
SwapFree:       16777216 kB
Dirty:                 0 kB
Writeback:             0 kB
AnonPages:        100056 kB
Mapped:             4488 kB
Shmem:              8184 kB
KReclaimable:    5051688 kB
Slab:               0 kB
SReclaimable:          0 kB
SUnreclaim:            0 kB
KernelStack:       36816 kB
PageTables:       113164 kB
NFS_Unstable:          0 kB
Bounce:                0 kB
WritebackTmp:          0 kB
CommitLimit:    859064848 kB
Committed_AS:   74072316 kB
VmallocTotal:   34359738367 kB
VmallocUsed:    13546056 kB
VmallocChunk:          0 kB
Percpu:           142400 kB
HardwareCorrupted:     0 kB
AnonHugePages:         0 kB
ShmemHugePages:        0 kB
ShmemPmdMapped:        0 kB
FileHugePages:         0 kB
FilePmdMapped:         0 kB
CmaTotal:              0 kB
CmaFree:               0 kB
HugePages_Total:       0
HugePages_Free:        0
HugePages_Rsvd:        0
HugePages_Surp:        0
Hugepagesize:       2048 kB
Hugetlb:               0 kB
DirectMap4k:    18957800 kB
DirectMap2M:    202948608 kB
DirectMap1G:    1389363200 kB

But here's the problem, /proc/swaps shows all of the swap as used:
Code:
# cat /proc/swaps
Filename                Type        Size    Used    Priority
none                                    virtual        16777216    16777216    0

Proxmox host details:
Code:
# pveversion --verbose
proxmox-ve: 6.2-2 (running kernel: 5.4.73-1-pve)
pve-manager: 6.2-15 (running version: 6.2-15/48bd51b6)
pve-kernel-5.4: 6.3-1
pve-kernel-helper: 6.3-1
pve-kernel-5.4.73-1-pve: 5.4.73-1
pve-kernel-5.4.34-1-pve: 5.4.34-2
ceph-fuse: 12.2.11+dfsg1-2.1+b1
corosync: 3.0.4-pve1
criu: 3.11-3
glusterfs-client: 5.5-3
ifupdown: 0.8.35+pve1
ksm-control-daemon: 1.3-1
libjs-extjs: 6.0.1-10
libknet1: 1.16-pve1
libproxmox-acme-perl: 1.0.5
libpve-access-control: 6.1-3
libpve-apiclient-perl: 3.0-3
libpve-common-perl: 6.2-4
libpve-guest-common-perl: 3.1-3
libpve-http-server-perl: 3.0-6
libpve-storage-perl: 6.2-10
libqb0: 1.0.5-1
libspice-server1: 0.14.2-4~pve6+1
lvm2: 2.03.02-pve4
lxc-pve: 4.0.3-1
lxcfs: 4.0.3-pve3
novnc-pve: 1.1.0-1
proxmox-backup-client: 1.0.1-1
proxmox-mini-journalreader: 1.1-1
proxmox-widget-toolkit: 2.3-10
pve-cluster: 6.2-1
pve-container: 3.2-3
pve-docs: 6.2-6
pve-edk2-firmware: 2.20200531-1
pve-firewall: 4.1-3
pve-firmware: 3.1-3
pve-ha-manager: 3.1-1
pve-i18n: 2.2-2
pve-qemu-kvm: 5.1.0-6
pve-xtermjs: 4.7.0-2
qemu-server: 6.2-20
smartmontools: 7.1-pve2
spiceterm: 3.1-1
vncterm: 1.6-2
zfsutils-linux: 0.8.5-pve1

Here's /proc/swaps on the hypervisor (correct):

Code:
# cat /proc/swaps
Filename                Type        Size    Used    Priority
/dev/zd16                               partition    67108860    0    -2

Any ideas?
 

denos

Active Member
Jul 27, 2015
82
39
38
I traced the bug to lxcfs:
Working: 4.0.3-pve2
Broken: 4.0.3-pve3

I think help is needed from a Proxmox team member on this one.
 

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