1 Reply Latest reply on Apr 12, 2012 5:23 PM by Dan_Intel

    DX79TO and VT-d + linux


      Hi all.


      I have brand new DX79TO board (v. AAG28805-400) with i7-3930K processor and 32GB RAM. The system shoud be a good host for virtual machines, but is NOT!

      For host OS I use Ubuntu 12.04 (also try 10.04) with latest 3.3 kernel (also try other kernels) and Vitualbox 4.1.10, for virtual machines I have also Ubuntu 10.04. All OS are 64bit.


      The problem is that virtual mashine is slow when I give it more than 2 cores. I use simple script which does some quick DB querys (cca. 5000q/sec) and the result is:

      - 1 core: 1.58 sec
      - 2 cores: 1.43 sec
      - 4 cores: 4.10 sec
      - 6 cores: 4.11 sec
      - 8 cores: 4.25 sec
      - 10 cores: 4.61 sec

      - 12 cores: 4.81 sec


      So with 4 cores machine is almost 3 times slower compare to 1 or 2 cores! On host system I get much better results (1.3-1.5 sec).


      For example, i have similar host mashine with DP67BA board and i7-2600 CPU. With same benchmark script and same virtual machine as above I get this results:

      - 1 core: 1.43 sec
      - 2 cores: 1.63 sec
      - 4 cores: 1.65 sec
      - 6 cores: 1.72 sec
      - 8 cores:  1.87 sec


      I read some informations about CPU bug on i7-3930K (VT-d), but it affects only C-1 stepping, my processor is C-2 stepping (model number: 00206D7). Is it possible that on DX79TO board VT-d is not supported also on C-2 stepping processors (in BIOS i see VT-d option, I try disable it and I get same results)? I have the latest BIOS (3/15/2012).


      Well maybe is also SW problem with either OS or virtualbox.


      I get this output with lshw command on host OS:

      generic:2 UNCLAIMED
      description: PIC

      product: Sandy Bridge I/O APIC


      .. so it seams that I/O APIC has no kernel driver. As far as i know I/O APIC is important part of multicore system, but if this will not work also host system should work slowly (but my is ok, just virtualization is problematic)?!


      Have someone similar problems? Any clues what's wrong?