[CentOS-virt] Nested KVM issue

Sun Aug 14 20:27:21 UTC 2016
Boris Derzhavets <bderzhavets at hotmail.com>

Reports  posted look good for me.  Config should provide the best available performance

for cloud VM (L2) on Compute Node.

 1.  Please, remind me what goes  wrong  from your standpoint ?

 2. Which CPU is installed on Compute Node && how much RAM ?

     Actually , my concern is :-

    Number_of_ Cloud_VMs  versus Number_CPU_Cores ( not threads)

    Please, check `top`  report   in regards of swap area size.



From: centos-virt-bounces at centos.org <centos-virt-bounces at centos.org> on behalf of Laurentiu Soica <laurentiu at soica.ro>
Sent: Sunday, August 14, 2016 3:06 PM
To: Discussion about the virtualization on CentOS
Subject: Re: [CentOS-virt] Nested KVM issue


1. <domain type='kvm' id='6'>
  <memory unit='KiB'>104857600</memory>
  <currentMemory unit='KiB'>104857600</currentMemory>
  <vcpu placement='static'>36</vcpu>
    <type arch='x86_64' machine='pc-i440fx-rhel7.0.0'>hvm</type>
    <boot dev='hd'/>
    <bootmenu enable='no'/>
  <cpu mode='host-passthrough'/>
  <clock offset='utc'/>
    <disk type='file' device='disk'>
      <driver name='qemu' type='qcow2' cache='unsafe'/>
      <source file='/var/lib/libvirt/images/baremetalbrbm_1.qcow2'/>
      <target dev='sda' bus='sata'/>
      <alias name='sata0-0-0'/>
      <address type='drive' controller='0' bus='0' target='0' unit='0'/>
    <controller type='scsi' index='0' model='virtio-scsi'>
      <alias name='scsi0'/>
      <address type='pci' domain='0x0000' bus='0x00' slot='0x04' function='0x0'/>
    <controller type='usb' index='0'>
      <alias name='usb'/>
      <address type='pci' domain='0x0000' bus='0x00' slot='0x01' function='0x2'/>
    <controller type='pci' index='0' model='pci-root'>
      <alias name='pci.0'/>
    <controller type='sata' index='0'>
      <alias name='sata0'/>
      <address type='pci' domain='0x0000' bus='0x00' slot='0x05' function='0x0'/>
    <interface type='bridge'>
      <mac address='00:f1:15:20:c5:46'/>
      <source network='brbm' bridge='brbm'/>
      <virtualport type='openvswitch'>
        <parameters interfaceid='654ad04f-fa0a-41dd-9d30-b84e702462fe'/>
      <target dev='vnet5'/>
      <model type='virtio'/>
      <alias name='net0'/>
      <address type='pci' domain='0x0000' bus='0x00' slot='0x03' function='0x0'/>
    <interface type='bridge'>
      <mac address='52:54:00:d3:c9:24'/>
      <source bridge='br57'/>
      <target dev='vnet6'/>
      <model type='rtl8139'/>
      <alias name='net1'/>
      <address type='pci' domain='0x0000' bus='0x00' slot='0x07' function='0x0'/>
    <serial type='pty'>
      <source path='/dev/pts/3'/>
      <target port='0'/>
      <alias name='serial0'/>
    <console type='pty' tty='/dev/pts/3'>
      <source path='/dev/pts/3'/>
      <target type='serial' port='0'/>
      <alias name='serial0'/>
    <input type='mouse' bus='ps2'/>
    <input type='keyboard' bus='ps2'/>
    <graphics type='vnc' port='5903' autoport='yes' listen=''>
      <listen type='address' address=''/>
      <model type='cirrus' vram='16384' heads='1'/>
      <alias name='video0'/>
      <address type='pci' domain='0x0000' bus='0x00' slot='0x02' function='0x0'/>
    <memballoon model='virtio'>
      <alias name='balloon0'/>
      <address type='pci' domain='0x0000' bus='0x00' slot='0x06' function='0x0'/>

[root at overcloud-novacompute-0 ~]# lsmod | grep kvm
kvm_intel             162153  70
kvm                   525409  1 kvm_intel

[root at overcloud-novacompute-0 ~]# cat /etc/nova/nova.conf | grep virt_type|grep -v '^#'

[root at overcloud-novacompute-0 ~]#  cat /etc/nova/nova.conf | grep  cpu_mode|grep -v '^#'


În dum., 14 aug. 2016 la 21:44, Boris Derzhavets <bderzhavets at hotmail.com<mailto:bderzhavets at hotmail.com>> a scris:

From: centos-virt-bounces at centos.org<mailto:centos-virt-bounces at centos.org> <centos-virt-bounces at centos.org<mailto:centos-virt-bounces at centos.org>> on behalf of Laurentiu Soica <laurentiu at soica.ro<mailto:laurentiu at soica.ro>>
Sent: Sunday, August 14, 2016 10:17 AM
To: Discussion about the virtualization on CentOS
Subject: Re: [CentOS-virt] Nested KVM issue

More details on the subject:

I suppose it is a nested KVM issue because it raised after I enabled the nested KVM feature. Without it, anyway, the second level VMs are unusable in terms of performance.

I am using CentOS 7 with:

kernel: 3.10.0-327.22.2.el7.x86_64

on both the baremetal and the compute VM.

Please, post

1) # virsh dumpxml  VM-L1  ( where on L1 level you expect nested KVM to appear)
2) Login into VM-L1 and run :-
    # lsmod | grep kvm
3) I need outputs from VM-L1 ( in case it is Compute Node )

# cat /etc/nova/nova.conf | grep virt_type
# cat /etc/nova/nova.conf | grep  cpu_mode


The only workaround now is to shutdown the compute VM and start it back from baremetal with virsh start.
A simple restart of the compute node doesn't help. It looks like the qemu-kvm process corresponding to the compute VM is the problem.


În dum., 14 aug. 2016 la 00:19, Laurentiu Soica <laurentiu at soica.ro<mailto:laurentiu at soica.ro>> a scris:

I have an OpenStack setup in virtual environment on CentOS 7.

The baremetal has nested KVM enabled and 1 compute node as a VM.

Inside the compute node I have multiple VMs running.

After about every 3 days the VMs get inaccessible and the compute node reports high CPU usage. The qemu-kvm process for each VM inside the compute node reports full CPU usage.

Please help me with some hints to debug this issue.

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