Virtualbox guests: Windows very fast, Linux very slow

Discussion in 'sandboxing & virtualization' started by Gullible Jones, Aug 19, 2014.

  1. Gullible Jones

    Gullible Jones Registered Member

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    Using Virtualbox 4.3.14 on a Compaq C700 with 2 GB of RAM, no VT-x. For legacy Windows stuff I use a Windows 2000 guess, and it performs better than native Win2k on similar hardware. (Probably scalability issues with Win2k, but still.) 30 second boot time, runs without any lag.

    Tried some Linux guests though, and they are astonishingly slow. 5+ minute boot times, crazy cursor lag, 99% CPU usage on both cores on the host. This is the case even with guest additions installed. I/O to the virtual hard drive is particularly slow, by looks less than 1/8 the speed on the host.

    Has anyone seen this? Any ideas? I know VT-x would help a lot, but it is not an option with this laptop, and right now (AFAIK) Virtualbox is the only open source player in town.
     
  2. J_L

    J_L Registered Member

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    Host OS? If it's Windows, I'm kinda surprised that 4.3.14 is even running.
     
  3. Gullible Jones

    Gullible Jones Registered Member

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    Host OS is Linux (SalixOS 14.1 x86-64, default kernel).
     
  4. luciddream

    luciddream Registered Member

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    It most definitely would. And judging by the figures you provided I'd say VT-d might help just as much. But regardless that still doesn't look right... something must be wrong. Though W2K does indeed run like greased lightning as Guest, not sure why, but you may be onto something there.
     
  5. Gullible Jones

    Gullible Jones Registered Member

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    So, a rather belated update: the problem seems to be dynamic volumes. Xubuntu 14.10, with 512 MB of RAM and no guest additions, is not exactly snappy on an 8 GB static volume, but it is much faster than on a 28 GB dynamic volume.

    I'm thinking:
    - Spinning disks + dynamic allocation = lots of fragmentation and seek delays
    - Less common filesystems like JFS (which I use) may take this especially badly
    - Dynamic volumes are best used for data storage etc., root volumes should be small and static

    Edit: also, more video RAM helps. At least 64 MB, preferably the full 128.

    Edit 2: this was actually two separate issues. Slow I/O was probably from the dynamic volume, cursor lag was from lack of allocated video RAM. I didn't realize video RAM was such an issue even for 2D desktops.
     
    Last edited: Dec 2, 2014
  6. sthmptn

    sthmptn Registered Member

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    I've stopped using vbox and am now happy enough to go fully with KVM but I agree above--when I last set up guests I got big improvements using: fixed disk (big difference like you say), enabling IO APIC, ramping up the processors and using max video memory. This gave a much, much snappier performance against the default settings.
     
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