Alert: Control Domain Memory Usage

[dave]

Hi, i still have this problem on 5 hosts in 2 pools. I increased the dom0 memory to 12GB and 16GB, but its still happening. XCP 8.0 and 8.1 involved. On hosts with more VMs it occures more often then on hosts with less VMs. Its happens between 40 - 140 days, depending on the number of VMs running.

Yes, ownvswitch has the greatest memory usage, but ist still only a small percentage. I still cant see, what eats up the memory. Restarting XAPI doensn`t change anything.

top - 18:37:06 up 144 days, 19:43,  1 user,  load average: 2.23, 2.12, 2.16
Tasks: 443 total,   1 running, 272 sleeping,   0 stopped,   0 zombie
%Cpu(s):  1.3 us,  1.7 sy,  0.0 ni, 95.7 id,  0.8 wa,  0.0 hi,  0.1 si,  0.4 st
KiB Mem : 12205932 total,    91920 free, 11932860 used,   181152 buff/cache
KiB Swap:  1048572 total,   807616 free,   240956 used.    24552 avail Mem

  PID USER      PR  NI    VIRT    RES    SHR S  %CPU %MEM     TIME+ COMMAND
 2248 root      10 -10 1302696 158708   9756 S   1.0  1.3   2057:54 ovs-vswitchd
 3018 root      20   0  597328  25804      4 S   0.3  0.2 635:40.46 xapi
 1653 root      20   0  255940  20628   1088 S   0.0  0.2   1517:12 xcp-rrdd
 1321 root      20   0  142596  15100   7228 S   0.3  0.1  40:49.02 message-switch
 6571 root      20   0  213720  12164   4920 S   0.0  0.1   9:30.58 python
 1719 root      20   0   62480   9980   3488 S   0.0  0.1 269:35.54 xcp-rrdd-xenpm
13506 root      20   0   43828   9652   2856 S   0.0  0.1   0:05.11 tapdisk
 1721 root      20   0  111596   8684   1592 S   0.0  0.1 337:51.20 xcp-rrdd-iostat
 2342 root      20   0  138220   8656   2744 S   0.0  0.1 218:17.74 xcp-networkd
 1639 root      20   0 1241012   8428   6024 S   0.0  0.1 150:25.56 multipathd
 6092 root      20   0   42428   7924   3924 S  17.2  0.1   2987:48 tapdisk
 1649 root      20   0   75116   6980   2192 S   0.0  0.1 294:06.89 oxenstored
 5436 root      10 -10   35432   6760   4112 S   0.0  0.1   0:00.03 iscsid
13898 root      20   0   40824   6648   2856 S   0.0  0.1   0:09.13 tapdisk
 3547 root      20   0   39852   5564   3376 S   0.7  0.0  54:01.72 tapdisk
 3006 root      20   0   40028   5460   2496 S  14.2  0.0  19:10.48 tapdisk
 1326 root      20   0   67612   5220   2840 S   0.0  0.0 529:23.01 forkexecd
 3027 root      20   0  108028   5176   5176 S   0.0  0.0   0:00.02 xapi-nbd
15298 root      20   0   39644   5156   3940 S   0.7  0.0 853:39.92 tapdisk
 3694 root      20   0  238044   5084   5084 S   0.0  0.0   0:01.39 python
 6945 root      20   0   39484   4860   3804 S  15.8  0.0 591:05.22 tapdisk
24422 root      20   0   44980   4844   4756 S   0.0  0.0   0:00.22 stunnel
11328 root      20   0   44980   4684   4640 S   0.0  0.0   0:00.06 stunnel
 2987 root      20   0   44980   4608   4440 S   0.0  0.0   0:00.29 stunnel
 6095 root      20   0   38768   4588   2912 S   0.0  0.0 764:33.14 tapdisk
 1322 root      20   0   69848   4388   3772 S   0.0  0.0   1:15.05 varstored-guard
14873 root      20   0   38688   4360   2744 S   0.0  0.0  57:33.78 tapdisk
 1329 root      20   0  371368   4244   3664 S   0.0  0.0   0:41.49 snapwatchd
 1328 root      20   0  112824   4212   4212 S   0.0  0.0   0:00.02 sshd
 2219 root      10 -10   44788   4004   3064 S   0.0  0.0 138:30.56 ovsdb-server
 3278 root      20   0  307316   3960   3764 S   0.0  0.0   3:15.34 stunnel
17064 root      20   0  153116   3948   3772 S   0.0  0.0   0:00.16 sshd
30189 root      20   0   38128   3716   2828 S   0.0  0.0  97:30.65 tapdisk

@olivierlambert Do you have an idea how to get to the root of this? Is it maybe possible to get some (paid) support to check this?

[olivierlambert]

Sounds like a memory leak. It's hard to pinpoint in general. I would say that investigating on 8.2 as soon it's out would be probably a better thing to do (it will be an LTS).

It will be out in beta soon

[inaki.martinez]

Just to add that us too have been experiencing the issue pointed out by Dave since we upgraded to 8.0. Even if the in place upgrade did bump the Dom0 memory from 4 to 8GB, we started to get out of memory errors on the pool master after an uptime of around 60 to 70 days.

Our current solution as mentioned in the thread too, is to icrease the memory for Dom0 to 32GBs but this does only buys us more time until the next reboot.

The main problem is that once this happens, backups start to fail and the only solution is to empty the host and reboot, which can be disruptive to some large VMs that don't seem to support live migration very well.

To add some more data, here is a graph of the memory consumption in the master of one of our pools, uptime starts at around week 33 and week 43 is current time (pending a reboot and memory increase for that host). This is a pool of three hosts and 80 vms.

Let me know if we can help with log data or anything else.

[olivierlambert]

Please migrate to 8.1 and report if you have the same behavior.

[stormi]

@inaki-martinez Could you find out if a specific program uses that memory?

[inaki.martinez]

@olivierlambert will upgrade our test environment and see if we can see the issue happening again.
@stormi there is nothing using particularly too much ram, listing processes by their RSS rss_usage.txt

[daKju]

@olivierlambert this still happens at 8.1 also
@stormi it seems that the memory is eating somewhere and doesn't point to specific program. @dave also described here https://xcp-ng.org/forum/post/31693

[stormi]

I'd be interested in accessing remotely any host that has this kind of high memory usage without any specific process being an obvious culprit, if someone can give me such access.

[dave]

@stormi I currently have this one:

top - 15:55:55 up 30 days, 19:31,  1 user,  load average: 0.13, 0.19, 0.23
Tasks: 645 total,   1 running, 437 sleeping,   0 stopped,   0 zombie
%Cpu(s):  0.7 us,  0.7 sy,  0.0 ni, 97.9 id,  0.5 wa,  0.0 hi,  0.0 si,  0.2 st
KiB Mem : 12205936 total,   159044 free,  6327592 used,  5719300 buff/cache
KiB Swap:  1048572 total,  1048572 free,        0 used.  5455076 avail Mem

  PID USER      PR  NI    VIRT    RES    SHR S  %CPU %MEM     TIME+ COMMAND
11785 root      20   0   38944   4516   3256 S   3.6  0.0  27:50.89 tapdisk
16619 root      20   0   71988  37640  35464 S   2.0  0.3   1048:44 tapdisk
 2179 root      10 -10 1302860 155032   9756 S   1.7  1.3 699:20.93 ovs-vswitchd
 8627 root      20   0   42496   8276   5896 S   1.3  0.1 645:07.94 tapdisk
12127 65572     20   0  220692  14508   9220 S   1.3  0.1 105:51.34 qemu-system-i38
15573 65567     20   0  228884  14880   9168 S   1.3  0.1 113:17.76 qemu-system-i38
16713 root      20   0   71244  37060  35636 S   1.3  0.3 431:04.58 tapdisk
17124 65565     20   0  253460  15536   9212 S   1.3  0.1 230:28.27 qemu-system-i38
  507 65547     20   0  204308  13576   9176 S   1.0  0.1 374:00.32 qemu-system-i38
 1348 65548     20   0  199188  15852   9268 S   1.0  0.1 478:44.62 qemu-system-i38
 1822 root      20   0  122268  15792   6292 S   1.0  0.1 251:54.49 xcp-rrdd-iostat
 3560 65549     20   0  236052  15696   9272 S   1.0  0.1 478:25.30 qemu-system-i38
 4049 65550     20   0  211476  13712   9096 S   1.0  0.1 374:53.29 qemu-system-i38
 9089 65566     20   0  225812  16328   9236 S   1.0  0.1 226:40.10 qemu-system-i38
19051 65555     20   0  213524  14960   9444 S   1.0  0.1 312:44.65 qemu-system-i38
22650 65540     20   0  231956  14016   9104 S   1.0  0.1 476:19.21 qemu-system-i38
28280 65543     20   0  284180  14356   9180 S   1.0  0.1 481:22.74 qemu-system-i38
28702 65544     20   0  194068  13636   9020 S   1.0  0.1 373:26.97 qemu-system-i38
28981 65568     20   0  174604  15528   9244 S   1.0  0.1 107:15.89 qemu-system-i38
29745 65541     20   0  171532  13792   9132 S   1.0  0.1 476:38.74 qemu-system-i38
 1244 root      20   0   67656   8252   4576 S   0.7  0.1 160:47.13 forkexecd
 4993 root      20   0  180476  10244   3608 S   0.7  0.1  50:10.80 mpathalert
 7194 root      20   0  162508   5052   3824 R   0.7  0.0   0:00.67 top
15180 root      20   0   44744  10500   9328 S   0.7  0.1  26:43.32 tapdisk
16643 65573     20   0  229908  14280   9220 S   0.7  0.1  66:42.94 qemu-system-i38
18769 root      20   0   46616  12316  10912 S   0.7  0.1 241:10.00 tapdisk
22133 65539     20   0   13.3g  16384   9180 S   0.7  0.1 374:26.35 qemu-system-i38
   10 root      20   0       0      0      0 I   0.3  0.0  47:35.79 rcu_sched
 2291 root      20   0  138300  16168   7660 S   0.3  0.1  65:30.99 xcp-networkd
 3029 root      20   0       0      0      0 I   0.3  0.0   0:02.12 kworker/6:0-eve
 3100 root      20   0   95448  17028   9280 S   0.3  0.1  76:30.01 xapi-storage-sc
 3902 root      20   0       0      0      0 I   0.3  0.0   0:07.16 kworker/u32:0-b
 3909 root      20   0       0      0      0 I   0.3  0.0   0:07.48 kworker/u32:4-b
 6663 root      20   0       0      0      0 S   0.3  0.0  70:40.93 kdmwork-253:0
 7826 root      20   0  193828   4224   3668 S   0.3  0.0   0:00.01 login
 8626 root      20   0   71368  37184  35636 S   0.3  0.3 345:42.82 tapdisk

Please contact me with a DM.

[stormi]

@dave The situation looks normal to me in this host, with a lot of RAM being used for buffers and cache, contrarily to the starved situation you posted about a month ago. Only half the RAM is counted as used. Is it more than normal?

[dave]

@stormi Of course, sorry. Thats strange, i would have expected the usage would be quite high after 30 days uptime - as it was every time the last year...The usage is quite low, on two Servers which were affected before, ATM.
Before the 30 days seen uptime, i did a yum update on 25.09.2020. A lot of driver and kernel packages were upated in this run.
I have another affected pool, which was restarted 7 days ago because of mem-consumption, but without updating. (lates yum update on 08.05.2020) i will keep an eye on it. Maybe some Updates for 8.1 released beetween 08.05.2020 and 25.09.2020 fixed this error. We will see.

[stormi]

@dave said in Alert: Control Domain Memory Usage:

Maybe some Updates for 8.1 released beetween 08.05.2020 and 25.09.2020 fixed this error. We will see.

Since that date the updates have been:

• microcode_ctl to fix CROSSTalk vulneratbilities (SRBDS), as well as a kernel patch to reduce the performance overhead of the new microcode
• Xen security updates, not supposed to have any impact on dom0 memory usage
• qemu security fixes that don't seem related to memory usage at first sight

All the fixes were very specific so I doubt that is what prevented the issue from occurring in your situation, but that remains a possibility.

[stormi]

Anyone having such high memory usage, please share the output of slabtop -o -s c, cat /proc/meminfo and top (sorted by decreasing MEM%, shortcut for that is M).

Previous messages in this thread also suggested two possible culprits:

• (unresponsive) CIFS mounts. Check for their presence.
• openvswitch. From recent output of top shared with us, it doesn't look like it's using that much RAM, but you may try to restart it: systemctl restart openvswitch.service

[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>