Alert: Control Domain Memory Usage

inaki.martinez

@stormi This is the info for the current pool master with memory issues. The machine had the last OOM event on October 12th.
Slabtop: slabopt.txt
meminfo: meminfo.txt
sorted top:

stormi

@inaki-martinez Thanks. Could you also share the output of ps aux? And what process got killed by the OOM-killer on Oct 12th?

Update: your situation seems to differ from that of @dave described in https://xcp-ng.org/forum/post/31693, because in his case there's almost no memory usage from processes where in your case a more significant part of the used memory is attributed to processes.

dave

I have found a host with around 7Gigs om mem used, mostly without a visible process for it.
This is a host which runs less VMs, so it takes longer to fill up the RAM.
slabtop.txt meminfo.txt
ps aux.txt

top - 12:15:02 up 60 days, 59 min,  2 users,  load average: 0.25, 0.13, 0.10
Tasks: 297 total,   1 running, 189 sleeping,   0 stopped,   0 zombie
%Cpu(s):  0.5 us,  0.4 sy,  0.0 ni, 98.6 id,  0.4 wa,  0.0 hi,  0.0 si,  0.1 st
KiB Mem : 12210160 total,  3879276 free,  7295660 used,  1035224 buff/cache
KiB Swap:  1048572 total,  1048572 free,        0 used.  4691716 avail Mem

  PID USER      PR  NI    VIRT    RES    SHR S  %CPU %MEM     TIME+ COMMAND
 2516 root      20   0  866796  92696  25116 S   0.3  0.8 222:40.81 xapi
 1947 root      10 -10  712372  89348   9756 S   0.7  0.7 594:52.86 ovs-vswitchd
 1054 root      20   0  102204  30600  15516 S   0.3  0.3  22:13.27 message-switch
 2515 root      20   0  493252  25328  12884 S   0.0  0.2 119:46.39 xenopsd-xc
 2527 root      20   0  244124  25128   8952 S   0.0  0.2   0:24.59 python
 1533 root      20   0  277472  23956   7928 S   0.0  0.2 155:35.64 xcp-rrdd
 2514 root      20   0   95448  19204  11588 S   0.0  0.2 100:44.55 xapi-storage-sc
 1069 root      20   0   69952  17980   9676 S   0.0  0.1   0:22.94 varstored-guard
 2042 root      20   0  138300  17524   9116 S   0.3  0.1  68:39.86 xcp-networkd
 2524 root      20   0  211576  17248   7728 S   0.0  0.1   7:57.55 python
 2041 root      20   0  223856  16836   7840 S   0.0  0.1   0:00.28 python
26502 65539     20   0  331284  16236   9340 S   1.0  0.1 580:03.42 qemu-system-i38
 5724 65540     20   0  208404  15400   9240 S   0.7  0.1 450:29.20 qemu-system-i38
 2528 root      20   0  108192  14760  10284 S   0.0  0.1   0:00.01 xapi-nbd
 9482 65537     20   0  316948  14204   9316 S   0.3  0.1 541:50.85 qemu-system-i38
24445 65541     20   0  247308  13704   9124 S   0.7  0.1  71:45.92 qemu-system-i38
 1649 root      20   0   62552  13340   6172 S   0.0  0.1  58:24.21 xcp-rrdd-xenpm
 1650 root      20   0  109848  13320   6388 S   0.0  0.1 102:33.45 xcp-rrdd-iostat
 1294 root      20   0  127660  11044   5848 S   0.0  0.1  43:57.60 squeezed
 1647 root      20   0  115764  10944   6008 S   0.0  0.1  47:06.07 xcp-rrdd-squeez
26131 root      20   0   45096  10920   3024 S   0.0  0.1  10065:02 tapdisk
 4781 root      20   0  180476  10816   5832 S   0.0  0.1  41:45.65 mpathalert
 1725 root      20   0  987212  10024   8116 S   0.0  0.1   0:02.70 lwsmd
25383 root      20   0  155244   9824   8488 S   0.0  0.1   0:00.06 sshd
 1068 root      20   0  222612   9756   5544 S   0.0  0.1  39:12.40 v6d
 1648 root      20   0  196692   9688   5364 S   0.0  0.1  38:58.31 xcp-rrdd-gpumon
 3198 root      20   0 4178388   9488   4160 S   0.0  0.1  22:03.95 stunnel
 1603 root      20   0 1187748   8476   6724 S   0.0  0.1   0:00.05 lwsmd
 1055 root      20   0   67656   8432   4764 S   0.0  0.1 118:55.38 forkexecd
 1691 root      20   0 1060428   7840   6256 S   0.0  0.1   0:00.01 lwsmd
 1073 root      20   0  112824   7752   6724 S   0.0  0.1   0:00.01 sshd
 1558 root      20   0  322832   7652   6292 S   0.0  0.1   2:47.05 multipathd
 1263 root      20   0   73568   7548   3620 S   0.0  0.1  52:55.82 oxenstored
 1651 root      20   0  774588   7144   5732 S   0.0  0.1   0:00.01 lwsmd
23598 root      20   0   67656   6664   2988 S   0.0  0.1   0:00.00 forkexecd
 1576 root      20   0 1016092   6348   4920 S   0.0  0.1   0:00.02 lwsmd
 5170 root      10 -10   34412   5784   4112 S   0.0  0.0   0:00.00 iscsid
23599 root      20   0   44980   5696   4968 S   0.0  0.0   0:00.00 stunnel
    1 root      20   0   43816   5460   3792 S   0.0  0.0  17:48.63 systemd
26109 root      20   0   39700   5396   3024 S   0.0  0.0 272:18.60 tapdisk
 1032 root      20   0  266820   5352   3284 S   0.0  0.0  31:45.39 rsyslogd
 1935 root      10 -10   44740   5260   3800 S   0.0  0.0  20:40.87 ovsdb-server
26226 root      20   0   39460   5160   3284 S   1.0  0.0 975:42.44 tapdisk
14571 root      20   0  196608   5044   4388 S   0.0  0.0   0:00.01 login
25491 root      20   0  162332   4676   3764 R   0.0  0.0   0:00.62 top
 5305 root      20   0   38944   4668   3024 S   0.3  0.0  88:02.03 tapdisk
 9231 root      20   0   38676   4528   3024 S   0.0  0.0  24:38.80 tapdisk
 1469 root      20   0   21428   4508   1764 S   0.0  0.0   9:47.96 cdrommon
24991 root      20   0  162116   4508   3664 S   0.0  0.0   0:00.73 top
14758 root      20   0  116504   4420   3008 S   0.0  0.0   0:00.02 bash
24342 root      20   0   38560   4412   3024 S   0.0  0.0   1:04.19 tapdisk
 1042 dbus      20   0   58120   4328   3824 S   0.0  0.0   1:14.70 dbus-daemon
 2049 root      20   0   63560   4288   2988 S   0.0  0.0   0:00.00 forkexecd
25437 root      20   0  116500   4264   2916 S   0.0  0.0   0:00.03 bash
 1064 root      20   0   24504   4008   3328 S   0.0  0.0   0:00.11 smartd
 6542 root      20   0  115968   3808   2932 S   0.0  0.0   0:23.13 sh

r1

@Dave @inaki-martinez for info, can you share # sar of the day it went OOM?

stormi

@dave So, at this point our theories are:

dom0 memory ballooning
a kernel memory leak
each of us being really bad at understanding RAM usage in dom0

Can you share the contents of your grub.cfg, the line starting with "Domain-0" in the output of xl top, and output of xe vm-param-list uuid={YOUR_DOM0_VM_UUID} | grep memory?

inaki.martinez

@stormi this is the current ps aux: ps-aux.txt
@r1 the sar file is too big to add it here but here is a link sar.txt (valid for a day), and the kernel oom message too messages.txt . From what I can see only around 3GB where accounted for when the OOM killer was triggered (Dom0 has 8GB of memory available).
In this case rsyslog was killed but I have seen xapi killed on other occasions. I can dig up the logs if they can help.

inaki.martinez

@stormi

grub.cfg grub.txt
xl top for Dom0
Domain-0 -----r 5461432 0.0 8388608 1.6 8388608 1.6 16 0 0 0 0 0 0 0 0 0 0
xe param list for Dom0 (memory)

                         memory-target ( RO): <unknown>
                       memory-overhead ( RO): 118489088
                     memory-static-max ( RW): 8589934592
                    memory-dynamic-max ( RW): 8589934592
                    memory-dynamic-min ( RW): 8589934592
                     memory-static-min ( RW): 4294967296
                      last-boot-record ( RO): '('struct' ('uuid' '5e1386d5-e2c9-47eb-8445-77674d76c803') ('allowed_operations' ('array')) ('current_operations' ('struct')) ('power_state' 'Running') ('name_label' 'Control domain on host: bc2-vi-srv03') ('name_description' 'The domain which manages physical devices and manages other domains') ('user_version' '1') ('is_a_template' ('boolean' '0')) ('is_default_template' ('boolean' '0')) ('suspend_VDI' 'OpaqueRef:NULL') ('resident_on' 'OpaqueRef:946c6678-044a-62ab-2a98-f8c93e34ade9') ('affinity' 'OpaqueRef:946c6678-044a-62ab-2a98-f8c93e34ade9') ('memory_overhead' '84934656') ('memory_target' '4294967296') ('memory_static_max' '4294967296') ('memory_dynamic_max' '4294967296') ('memory_dynamic_min' '4294967296') ('memory_static_min' '4294967296') ('VCPUs_params' ('struct')) ('VCPUs_max' '48') ('VCPUs_at_startup' '48') ('actions_after_shutdown' 'destroy') ('actions_after_reboot' 'destroy') ('actions_after_crash' 'destroy') ('consoles' ('array' 'OpaqueRef:aa16584e-48c6-70a3-98c0-a2ee63b3cfa4' 'OpaqueRef:01efe105-d6fe-de5e-e214-9c6e2b5be498')) ('VIFs' ('array')) ('VBDs' ('array')) ('crash_dumps' ('array')) ('VTPMs' ('array')) ('PV_bootloader' '') ('PV_kernel' '') ('PV_ramdisk' '') ('PV_args' '') ('PV_bootloader_args' '') ('PV_legacy_args' '') ('HVM_boot_policy' '') ('HVM_boot_params' ('struct')) ('HVM_shadow_multiplier' ('double' '1')) ('platform' ('struct')) ('PCI_bus' '') ('other_config' ('struct' ('storage_driver_domain' 'OpaqueRef:166e5128-4906-05cc-bb8d-ec99a3c13dc0') ('is_system_domain' 'true'))) ('domid' '0') ('domarch' 'x64') ('last_boot_CPU_flags' ('struct')) ('is_control_domain' ('boolean' '1')) ('metrics' 'OpaqueRef:2207dad4-d07f-d7f9-9ebb-796072aa37e1') ('guest_metrics' 'OpaqueRef:NULL') ('last_booted_record' '') ('recommendations' '') ('xenstore_data' ('struct')) ('ha_always_run' ('boolean' '0')) ('ha_restart_priority' '') ('is_a_snapshot' ('boolean' '0')) ('snapshot_of' 'OpaqueRef:NULL') ('snapshots' ('array')) ('snapshot_time' ('dateTime.iso8601' '19700101T00:00:00Z')) ('transportable_snapshot_id' '') ('blobs' ('struct')) ('tags' ('array')) ('blocked_operations' ('struct')) ('snapshot_info' ('struct')) ('snapshot_metadata' '') ('parent' 'OpaqueRef:NULL') ('children' ('array')) ('bios_strings' ('struct')) ('protection_policy' 'OpaqueRef:NULL') ('is_snapshot_from_vmpp' ('boolean' '0')) ('snapshot_schedule' 'OpaqueRef:NULL') ('is_vmss_snapshot' ('boolean' '0')) ('appliance' 'OpaqueRef:NULL') ('start_delay' '0') ('shutdown_delay' '0') ('order' '0') ('VGPUs' ('array')) ('attached_PCIs' ('array')) ('suspend_SR' 'OpaqueRef:NULL') ('version' '0') ('generation_id' '') ('hardware_platform_version' '0') ('has_vendor_device' ('boolean' '0')) ('requires_reboot' ('boolean' '0')) ('reference_label' ''))'
                                memory (MRO): <not in database>

stormi

@inaki-martinez According to this log, 2GB of Resident Set Size was freed by killing rsyslog. This is a lot for such a system service.

JeffBerntsen

@stormi I seem to remember running across a similar problem on a RHEL system. Since XCP-ng is based on Centos which is pretty much the same thing, could it be related to this: https://bugzilla.redhat.com/show_bug.cgi?id=1663267

stormi

@JeffBerntsen this could be indeed. Advisory for the fix is https://access.redhat.com/errata/RHSA-2020:1000. I'll consider a backport.

@inaki-martinez I think dom0 memory ballooning (if that is even a thing... I need to confirm) is ruled out in your case. The sum of the RSS values for all processes (which is a simplistic and overestimating way of determining the RAM usage for all processes, due to shared memory), is around 1.5GB which leaves more than 4.5GB unexplained.

olivierlambert

RHSA-2020:1000 is an interesting lead, indeed

daKju

@stormi
i have the problem on a PoolMaster with 2 running VM's with memory alerts.
here are some infos. may you find something.

slabtop.txt
xehostparamlist.txt
xltop.txt
meminfo.txt
top.txt
grub.cfg.txt

sorry, can't add images. it seems there is something broken with some node modules.

stormi

@daKju Thanks. What version of XCP-ng? Does restarting the rsyslog service or the openvswitch release RAM?

daKju

@stormi
we have 8.1
I haven't start yet the services. can the openvswitch service safely restart without any impact?
nothing changed after rsyslog restart

stormi

@daKju I must admit I can't guarantee that it is perfectly safe. It will at least induce a small network downtime.

dave

Don`t restart openvswitch, if you have active iSCSI storage attached.

stormi

@dave since you're here, can you share the contents of your grub.cfg, the line starting with "Domain-0" in the output of xl top, and the output of xe vm-param-list uuid={YOUR_DOM0_VM_UUID} | grep memory?

And if your offer for remote access to a server to try and find where the missing memory is being used still stands, I'm interested.

stormi

Another lead, although quite old: https://serverfault.com/questions/520490/very-high-memory-usage-but-not-claimed-by-any-process

In that situation the memory was seemingly taken by operations related to LVM, and stopping all LVM operations released the memory. Not easy to test in production though.

dave

Current Top:

top - 15:38:00 up 62 days,  4:22,  2 users,  load average: 0.06, 0.08, 0.08
Tasks: 295 total,   1 running, 188 sleeping,   0 stopped,   0 zombie
%Cpu(s):  0.6 us,  0.0 sy,  0.0 ni, 99.4 id,  0.0 wa,  0.0 hi,  0.0 si,  0.0 st
KiB Mem : 12210160 total,  3596020 free,  7564312 used,  1049828 buff/cache
KiB Swap:  1048572 total,  1048572 free,        0 used.  4420052 avail Mem

  PID USER      PR  NI    VIRT    RES    SHR S  %CPU %MEM     TIME+ COMMAND
 2516 root      20   0  888308 123224  25172 S   0.0  1.0 230:49.43 xapi
 1947 root      10 -10  712372  89348   9756 S   0.0  0.7 616:24.82 ovs-vswitc+
 1054 root      20   0  102204  30600  15516 S   0.0  0.3  23:00.23 message-sw+
 2515 root      20   0  493252  25388  12884 S   0.0  0.2 124:03.44 xenopsd-xc
 2527 root      20   0  244124  25128   8952 S   0.0  0.2   0:24.59 python
 1533 root      20   0  277472  23956   7928 S   0.0  0.2 161:16.62 xcp-rrdd
 2514 root      20   0   95448  19204  11588 S   0.0  0.2 104:18.98 xapi-stora+
 1069 root      20   0   69952  17980   9676 S   0.0  0.1   0:23.74 varstored-+
 2042 root      20   0  138300  17524   9116 S   0.0  0.1  71:06.89 xcp-networ+
 2524 root      20   0  211832  17248   7728 S   0.0  0.1   8:15.16 python
 2041 root      20   0  223856  16836   7840 S   0.0  0.1   0:00.28 python
26502 65539     20   0  334356  16236   9340 S   0.0  0.1 603:42.74 qemu-syste+
 5724 65540     20   0  208404  15400   9240 S   0.0  0.1 469:19.79 qemu-syste+
 2528 root      20   0  108192  14760  10284 S   0.0  0.1   0:00.01 xapi-nbd
 9482 65537     20   0  316948  14204   9316 S   0.0  0.1 560:47.71 qemu-syste+
24445 65541     20   0  248332  13704   9124 S   0.0  0.1  90:45.58 qemu-syste+
 1649 root      20   0   62552  13340   6172 S   0.0  0.1  60:28.97 xcp-rrdd-x+

Requested Files:

xl top.txt
dom0 param list.txt
grub.cfg.txt

dave

@stormi Usualy i migrate all vms of affected hosts to others, when memory is nearly full. But that does not free any memory. Could LVM operations be still the happening, with no VMs running?