[ovirt-users] VM get stuck randomly

[Nir Soffer]

On Thu, Mar 24, 2016 at 7:51 PM, Christophe TREFOIS
<christophe.trefois at uni.lu> wrote:
> Hi Nir,
>
> And the second one is down now too. see some comments below.
>
>> On 13 Mar 2016, at 12:51, Nir Soffer <nsoffer at redhat.com> wrote:
>>
>> On Sun, Mar 13, 2016 at 9:46 AM, Christophe TREFOIS
>> <christophe.trefois at uni.lu> wrote:
>>> Dear all,
>>>
>>> I have a problem since couple of weeks, where randomly 1 VM (not always the same) becomes completely unresponsive.
>>> We find this out because our Icinga server complains that host is down.
>>>
>>> Upon inspection, we find we can’t open a console to the VM, nor can we login.
>>>
>>> In oVirt engine, the VM looks like “up”. The only weird thing is that RAM usage shows 0% and CPU usage shows 100% or 75% depending on number of cores.
>>> The only way to recover is to force shutdown the VM via 2-times shutdown from the engine.
>>>
>>> Could you please help me to start debugging this?
>>> I can provide any logs, but I’m not sure which ones, because I couldn’t see anything with ERROR in the vdsm logs on the host.
>>
>> I would inspect this vm on the host when it happens.
>>
>> What is vdsm cpu usage? what is the qemu process (for this vm) cpu usage?
>
> vdsm cpu usage is going up and down to 15%.
>
> qemu process usage for the VM was 0, except for 1 of the threads “stuck” at 100%, rest was idle.

0% may be a deadlock, 100% a thread stuck in endless loop, but this is
just a wild guess.

>
>>
>> strace output of this qemu process (all threads) or a core dump can help qemu
>> developers to understand this issue.
>
> I attached an strace on the process for:
>
> qemu     15241 10.6  0.4 4742904 1934988 ?     Sl   Mar23 131:41 /usr/libexec/qemu-kvm -name test-ubuntu-uni-lu -S -machine pc-i440fx-rhel7.2.0,accel=kvm,usb=off -cpu SandyBridge -m size=4194304k,slots=16,maxmem=4294967296k -realtime mlock=off -smp 4,maxcpus=64,sockets=16,cores=4,threads=1 -numa node,nodeid=0,cpus=0-3,mem=4096 -uuid 754871ec-0339-4a65-b490-6a766aaea537 -smbios type=1,manufacturer=oVirt,product=oVirt Node,version=7-2.1511.el7.centos.2.10,serial=4C4C4544-0048-4610-8052-B4C04F575831,uuid=754871ec-0339-4a65-b490-6a766aaea537 -no-user-config -nodefaults -chardev socket,id=charmonitor,path=/var/lib/libvirt/qemu/domain-test-ubuntu-uni-lu/monitor.sock,server,nowait -mon chardev=charmonitor,id=monitor,mode=control -rtc base=2016-03-23T22:06:01,driftfix=slew -global kvm-pit.lost_tick_policy=discard -no-hpet -no-shutdown -boot strict=on -device piix3-usb-uhci,id=usb,bus=pci.0,addr=0x1.0x2 -device virtio-scsi-pci,id=scsi0,bus=pci.0,addr=0x4 -device virtio-serial-pci,id=virtio-serial0,max_ports=16,bus=pci.0,addr=0x5 -drive if=none,id=drive-ide0-1-0,readonly=on,format=raw,serial= -device ide-cd,bus=ide.1,unit=0,drive=drive-ide0-1-0,id=ide0-1-0 -drive file=/rhev/data-center/00000002-0002-0002-0002-0000000003d5/8253a89b-651e-4ff4-865b-57adef05d383/images/9d60ae41-bf17-48b4-b0e6-29625b248718/47a6916c-c902-4ea3-8dfb-a3240d7d9515,if=none,id=drive-virtio-disk0,format=qcow2,serial=9d60ae41-bf17-48b4-b0e6-29625b248718,cache=none,werror=stop,rerror=stop,aio=threads -device virtio-blk-pci,scsi=off,bus=pci.0,addr=0x6,drive=drive-virtio-disk0,id=virtio-disk0,bootindex=1 -netdev tap,fd=108,id=hostnet0,vhost=on,vhostfd=109 -device virtio-net-pci,netdev=hostnet0,id=net0,mac=00:1a:4a:e5:12:0f,bus=pci.0,addr=0x3,bootindex=2 -chardev socket,id=charchannel0,path=/var/lib/libvirt/qemu/channels/754871ec-0339-4a65-b490-6a766aaea537.com.redhat.rhevm.vdsm,server,nowait -device virtserialport,bus=virtio-serial0.0,nr=1,chardev=charchannel0,id=channel0,name=com.redhat.rhevm.vdsm -chardev socket,id=charchannel1,path=/var/lib/libvirt/qemu/channels/754871ec-0339-4a65-b490-6a766aaea537.org.qemu.guest_agent.0,server,nowait -device virtserialport,bus=virtio-serial0.0,nr=2,chardev=charchannel1,id=channel1,name=org.qemu.guest_agent.0 -device usb-tablet,id=input0 -vnc 10.79.2.2:76,password -device cirrus-vga,id=video0,bus=pci.0,addr=0x2 -device virtio-balloon-pci,id=balloon0,bus=pci.0,addr=0x7 -msg timestamp=on
>
> http://paste.fedoraproject.org/344756/84131214

You connected only to one thread. I would try to use -f to see all threads,
or connect with gdb and get a backtrace of all threads.

Adding Kevin to suggest how to continue.

I think we need a qemu bug for this.

Nir

>
> This is CentOS 7.2, latest patches and latest 3.6.4 oVirt.
>
> Thank you for any help / pointers.
>
> Could it be memory ballooning?
>
> Best,
>
>>
>>>
>>> The host is running
>>>
>>> OS Version:             RHEL - 7 - 1.1503.el7.centos.2.8
>>> Kernel Version: 3.10.0 - 229.14.1.el7.x86_64
>>> KVM Version:            2.1.2 - 23.el7_1.8.1
>>> LIBVIRT Version:        libvirt-1.2.8-16.el7_1.4
>>> VDSM Version:   vdsm-4.16.26-0.el7.centos
>>> SPICE Version:  0.12.4 - 9.el7_1.3
>>> GlusterFS Version:      glusterfs-3.7.5-1.el7
>>
>> You are running old versions, missing lot of fixes. Nothing specific
>> to your problem
>> but this lower the chance to get a working system.
>>
>> It would be nice if you can upgrade to ovirt-3.6 and report if it made
>> any change.
>> Or at lest latest ovirt-3.5.
>>
>>> We use a locally exported gluster as storage domain (eg, storage is on the same machine exposed via gluster). No replica.
>>> We run around 50 VMs on that host.
>>
>> Why use gluster for this? Do you plan to add more gluster servers in the future?
>>
>> Nir
>