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Thread: Can't fully utilize CPU

  1. #1
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    Default Can't fully utilize CPU

    I have a 48 core Dell Poweredge R815 (4 chips x 12 cores) and I can't seem to use more than 33% of the CPU with a single VM. I've got a Windows Server 2008 KVM installed and I've been playing with the CPU/core settings and for some reason it seem like each Core I add utilizes 1 physical core. The problem with this is Proxmox has a max of 16 and this server has 48 meaning my VM can only utilize 33% of the CPU. When I run the VM at 100% CPU the node is only running 33%.

    Is this a limitation of the software or is something not working right? I was under the impression no matter how many virtual CPUs/Cores you assign the VM it should be able to use 100% of the physical CPU available.

    I am using the most recent version of Proxmox.

    Has anyone else had this issue?

  2. #2
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    Default Re: Can't fully utilize CPU

    Quote Originally Posted by ymmot04 View Post
    The problem with this is Proxmox has a max of 16
    That is the maximum cores, which is multiplied by the number of sockets you assign!

    So you can simply assign 4 socket each using 12 cores (= 48 threads)

  3. #3
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    Default Re: Can't fully utilize CPU

    does it work if you enter the values (4 sockets, 12 cores) in the VMID.conf file? (see /etc/qemu-server).

    and also post the output of 'pveversion -v'
    Best regards,
    Tom

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  4. #4
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    Default Re: Can't fully utilize CPU

    It does not work if I put those values in the configuration file. I tried with 4 sockets, 12 cores, and also 4 sockets, 5 cores. I get this error in the log.

    "VM 101 start failed: command '/usr/bin/kvm -monitor unix:/var/run/qemu-server/101.mon,server,nowait -vnc unix:/var/run/qemu-server/101.vnc,password -pidfile /var/run/qemu-server/101.pid -daemonize -usbdevice tablet -name Server2008 -smp sockets=4,cores=5 -nodefaults -boot menu=on -vga cirrus -tdf -localtime -rtc-td-hack -k en-us -drive file=/var/lib/vz/images/101/vm-101-disk-1.raw,if=ide,index=0,cache=none,boot=on -drive file=/var/lib/vz/template/iso/server2008.iso,if=ide,index=2,media=cdrom -m 64000 -netdev type=tap,id=vlan0d0,ifname=tap101i0d0,script=/var/lib/qemu-server/bridge-vlan -device rtl8139,mac=2A:564:36:39:B2,netdev=vlan0d0 -id 101 -cpuunits 1000' failed with exit code 1"

    If I reduce it back to 4 sockets, 4 cores it starts fine.

    'pveversion -v' returns:

    "pve-manager: 1.8-15 (pve-manager/1.8/5754)
    running kernel: 2.6.32-4-pve
    proxmox-ve-2.6.32: 1.8-32
    pve-kernel-2.6.32-4-pve: 2.6.32-32
    qemu-server: 1.1-30
    pve-firmware: 1.0-11
    libpve-storage-perl: 1.0-16
    vncterm: 0.9-2
    vzctl: 3.0.24-1pve4
    vzdump: 1.2-11
    vzprocps: 2.0.11-1dso2
    vzquota: 3.0.11-1
    pve-qemu-kvm: 0.14.0-2
    ksm-control-daemon: 1.0-5"

  5. #5
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    Default Re: Can't fully utilize CPU

    This is a fresh install that I am testing on BTW. I also tried updating everything:

    "pve-manager: 1.8-17 (pve-manager/1.8/5948)
    running kernel: 2.6.32-4-pve
    proxmox-ve-2.6.32: 1.8-33
    pve-kernel-2.6.32-4-pve: 2.6.32-33
    qemu-server: 1.1-30
    pve-firmware: 1.0-11
    libpve-storage-perl: 1.0-17
    vncterm: 0.9-2
    vzctl: 3.0.26-1pve4
    vzdump: 1.2-12
    vzprocps: 2.0.11-2
    vzquota: 3.0.11-1
    pve-qemu-kvm: 0.14.0-3
    ksm-control-daemon: 1.0-5"

    Still get this error:

    "VM 101 start failed: command '/usr/bin/kvm -monitor unix:/var/run/qemu-server/101.mon,server,nowait -vnc unix:/var/run/qemu-server/101.vnc,password -pidfile /var/run/qemu-server/101.pid -daemonize -usbdevice tablet -name Server2008 -smp sockets=4,cores=5 -nodefaults -boot menu=on -vga cirrus -tdf -localtime -rtc-td-hack -k en-us -drive file=/var/lib/vz/images/101/vm-101-disk-1.raw,if=ide,index=0,cache=none,boot=on -drive file=/var/lib/vz/template/iso/server2008.iso,if=ide,index=2,media=cdrom -m 64000 -netdev type=tap,id=vlan0d0,ifname=tap101i0d0,script=/var/lib/qemu-server/bridge-vlan -device rtl8139,mac=2A:564:36:39:B2,netdev=vlan0d0 -id 101 -cpuunits 1000' failed with exit code 1"

  6. #6
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    Default Re: Can't fully utilize CPU

    Seems to be a KVM bug. Already tested wit kernel 2.6.35?

  7. #7
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    Default Re: Can't fully utilize CPU

    I have not. I'll give it a try Tuesday and let you know the results.

  8. #8
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    Default Re: Can't fully utilize CPU

    Updated to 2.6.35 and now the virtual machine will start with 4 sockets and 12 cores if I manually enter it in the configuration. Thanks for the help guys!

    Any idea whether the 16 socket limitation is going to be removed from the gui?

  9. #9
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    Default Re: Can't fully utilize CPU

    Quote Originally Posted by ymmot04 View Post
    Any idea whether the 16 socket limitation is going to be removed from the gui?
    We will remove that in V2.0

  10. #10
    Join Date
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    Default Re: Can't fully utilize CPU

    you can change it in:

    /usr/share/pve-manager/root/qemu/index.htm

    my $maxcpus = 48;


    (i have also a r815

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