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Thread: KVM Virtualization Performance With Linux 2.6.31

  1. #1
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    Default KVM Virtualization Performance With Linux 2.6.31

    Phoronix: KVM Virtualization Performance With Linux 2.6.31

    Earlier this month at the Red Hat Summit where Red Hat Enterprise Linux 5.4 was released with support for the Kernel-based Virtual Machine. At this Red Hat event, virtualization -- particularly KVM -- and cloud computing were the most talked about topics. But how is KVM performing these days? With new virtualization refinements going into almost every new Linux kernel release, we have published a new set of KVM benchmarks using the Linux 2.6.31 kernel, to provide updated numbers against our KVM benchmarks from last year and our Core i7 virtualization numbers. This time around, we are also using a Phenom II processor for testing out the AMD-V technology.

    http://www.phoronix.com/vr.php?view=14201

  2. #2
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    What about a comparison of different virtual machines, let's say:

    qemu-kvm vs. VirtualBox (with guest additions) vs. VMWare client (with guest additions).

    By the way. Was the virtual harddisk a file or a block device?

  3. #3
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    I reinstalled Ubuntu with the latest Ubuntu 9.10 yesterday. My virtual machines was much slower than 9.04 when it comes to i/o performance. Something is wrong with the virtualization stack in 9.10. I have now switched back to 9.04.

    Someone should do the test for 9.04 kvm vs 9.10 kvm.

  4. #4
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    Arrow Bug

    SQLite though did extremely well in a virtualized setting due to a bug within EXT4 / Linux 2.6.31
    What bug are you talking about? Are you meaning that is a possible bug?

    Raine

  5. #5
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    Quote Originally Posted by Raine View Post
    What bug are you talking about? Are you meaning that is a possible bug?
    I think the only way the performance could go *UP* by that much, is that if the virtualization layer isn't properly synchronizing writes or locking or something like that from guest to host, which is almost certainly a serious bug.

  6. #6
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    I think there is an issue with VirtIO in that version of Ubuntu...

    The I/O benchmarks are really not representative of a proper KVM setup. I don't know why they published these benchmarks.
    Without VirtIO all the network and disk stuff is horrendous, a Google search will tell you that. They really should have used Fedora for this benchmark as well. Ubuntu has always been dodgy in terms of virtualization setups (something is always broken in my experience).
    Check out the KVM enhancements in Fedora 12! Wow!
    Last edited by DDevine; 09-21-2009 at 07:20 PM.

  7. #7

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    Quote Originally Posted by hubick View Post
    I think the only way the performance could go *UP* by that much, is that if the virtualization layer isn't properly synchronizing writes or locking or something like that from guest to host, which is almost certainly a serious bug.
    It's not a virtualization bug it's a flaw in the testing.
    What's happening is that the host is caching the writes so the data is not being written right away so it would appear to be faster.

  8. #8

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    Quote Originally Posted by phoronix View Post
    Phoronix: KVM Virtualization Performance With Linux 2.6.31

    Earlier this month at the Red Hat Summit where Red Hat Enterprise Linux 5.4 was released with support for the Kernel-based Virtual Machine. At this Red Hat event, virtualization -- particularly KVM -- and cloud computing were the most talked about topics. But how is KVM performing these days? With new virtualization refinements going into almost every new Linux kernel release, we have published a new set of KVM benchmarks using the Linux 2.6.31 kernel, to provide updated numbers against our KVM benchmarks from last year and our Core i7 virtualization numbers. This time around, we are also using a Phenom II processor for testing out the AMD-V technology.

    http://www.phoronix.com/vr.php?view=14201
    Testing it on Ubuntu probably won't yield the best results.
    You might want to try on RHEL 5.4 where it's been optimized or even on Fedora 11/12

    There's lots of optimizations to look at, from setting the IO scheduler to be deadline in the host, to using huge pages, cache settings etc.
    Have a look at the video here
    http://www.redhat.com/promo/summit/2009/highlights/ then click on the "Summit sessions" tab and then virtualization video

  9. #9
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    What is the outcome of this test?
    Software in a VM runs slower - what a suprise ;-)

    Is there a benefit of the AMD-V cpu features? How does it compare to Intel? So many interesting questions but the article has not a single answer - just meaningless numbers :-(

    (Please correct me if I did not see the conclusion of the article)

  10. #10
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    Quote Originally Posted by mibo View Post
    What is the outcome of this test?
    Software in a VM runs slower - what a suprise ;-)
    Wrong, according to the test SQLite ran magnitudes better under VM that native. Most CPU-intensive tasks were just as fast under VM, most hard-disk-intensive tasks were slower under VM. This would imo hint towards a need to develop better virtualization technology for hard disks.

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