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Xen Linux Guests Could Be Faster With Linux 4.13

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  • Xen Linux Guests Could Be Faster With Linux 4.13

    Phoronix: Xen Linux Guests Could Be Faster With Linux 4.13

    The Xen feature updates have been submitted for the Linux 4.13 kernel merge window...

    http://www.phoronix.com/scan.php?pag...For-Linux-4.13

  • #2
    This is good for Ryzen builds. KVM is not a good option for Ryzen w/GPU passthrough - having NPT enabled hogs the GPU performance, while NPT=0 fixes this GPU problem but the CPU beguns having massive periodic lag spikes.
    XEN does not have this issue with NPT and has a stable GPU passthrough with Ryzen.

    However only works for Radeon GPUs at the moment, since Nvidia consumer GPUs lock themselves when they detect an hypervisor (for which KVM has a workaround but not XEN)....

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    • #3
      Originally posted by monraaf View Post
      This is good for Ryzen builds. KVM is not a good option for Ryzen w/GPU passthrough - having NPT enabled hogs the GPU performance, while NPT=0 fixes this GPU problem but the CPU beguns having massive periodic lag spikes.
      We are trying to repro this in house in case we can come up with ideas re: why NPT might be affecting KVM but not Zen. Until last week this was apparently being considered as a general Ryzen problem rather than being specific to KVM, so hopefully the additional focus should help to find the problem.

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      • #4
        Interesting how Nvidia locks out hypervisors just to upsell to their more expensive Quadro cards.. That´s what i always liked with AMD hardware, they just allow you do perform any action the hardware is capable of.. Like having 10bit output surfaces and such!

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        • #5
          Originally posted by bridgman View Post

          We are trying to repro this in house in case we can come up with ideas re: why NPT might be affecting KVM but not Xen. Until last week this was apparently being considered as a general Ryzen problem rather than being specific to KVM, so hopefully the additional focus should help to find the problem.
          That is good and I hope you guys can find where the problem lies and fix that issue so that we can have options.
          Personally I know people that are considering not buying Zen right now while this issue is still unsolved, myself included, but we are all hoping it will be fixed soon.

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          • #6
            I'm not necessarily saying we will be the ones to fix it, but at least hoping we can help to find the problem.

            The main point I am trying to make is that before last week I don't think anyone was looking at it, since the KVM community had concluded it was a Ryzen issue (without our knowledge) and it was not on our radar as a problem at all.

            I just happened to notice a discussion on a Reddit thread (or maybe someone @bridgman'ed me), started asking questions, and one of the folks on the thread was nice enough to run the same test on Xen and realize that the performance drop was a KVM-specific issue.

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            • #7
              Originally posted by Spacefish View Post
              Interesting how Nvidia locks out hypervisors just to upsell to their more expensive Quadro cards.. That´s what i always liked with AMD hardware, they just allow you do perform any action the hardware is capable of.. Like having 10bit output surfaces and such!
              pretty sure this is not legal in the EU and you can get them to fine nvidia.

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              • #8
                Originally posted by cj.wijtmans View Post
                pretty sure this is not legal in the EU and you can get them to fine nvidia.
                Why would it be illegal? Artificially gimping cheap products for market segmentation is pretty commonplace.

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                • #9
                  Originally posted by chithanh View Post
                  Why would it be illegal? Artificially gimping cheap products for market segmentation is pretty commonplace.
                  EU has a lot more laws than US about this sort of thing.

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