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    [XCP-ng 8] max_grant_frames reached

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    • olivierlambertO Offline
      olivierlambert Vates 🪐 Co-Founder CEO
      last edited by

      But is it causing any issue in the VM?

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      • C Offline
        cfischer @olivierlambert
        last edited by olivierlambert

        @olivierlambert: Are you asking for issues with the VM? Yes, the issue is that I get round about 7.5 of 9 vif if I have 4 vcpu due to the lack of grants.

        I've freshly installed and updated OL7 and Debian9 using the provided templates.

        13:19 xs1 ~]# xl list
        Name                                        ID   Mem VCPUs      State   Time(s)
        Domain-0                                     0  1840     4     r-----    4892.2
        ER1-de.egr.lan                               1   512     4     -b----      86.5
        Debian Stretch 9.0 (1)                       7   511     4     -b----      14.5
        Oracle Linux 7 (1)                           9  4095     4     -b----      71.2
        [13:19 xs1 ~]# xen-diag gnttab_query_size 0
        domid=0: nr_frames=1, max_nr_frames=64
        [13:19 xs1 ~]# xen-diag gnttab_query_size 1
        domid=1: nr_frames=32, max_nr_frames=32
        [13:19 xs1 ~]# xen-diag gnttab_query_size 7
        domid=7: nr_frames=5, max_nr_frames=32
        [13:19 xs1 ~]# xen-diag gnttab_query_size 9
        domid=9: nr_frames=5, max_nr_frames=32
        

        Grants for domU are always 32. What is causing the grants limit?

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        • C Offline
          cfischer @olivierlambert
          last edited by cfischer

          @olivierlambert: I've read since 4.10 it is a domU configuration via max_grant_frames parameter. Since XCP-ng has no config files per domU, how can I set domU parameter?

          I've tried it via

          xe vm-param-set platform:max_grant_frames=64 uuid=b61297e6-a413-135a-fa1e-647b547247ef
          

          but no success.

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          • olivierlambertO Offline
            olivierlambert Vates 🪐 Co-Founder CEO
            last edited by

            1. Please use Markdown syntax for code/console blocks (I edited your post)
            2. Sorry I don't understand the problem you have, can you rephrase?
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            • C Offline
              cfischer @olivierlambert
              last edited by

              @olivierlambert: The problem is that there are not enough grants for creating queues for 9 vif on a system running 4 vcpu. Trying to create the 4th queue for vif-7 raises a max_grant_frames reached error. The netfront driver could create only 3 of 4 queues for vif-7 and 0 queues for vif-8, which is configured in Xen but therefore not present in the guest.

              That is not a problem of the "Other media install" template, all created VMs (different templates, different OSs) have the same issue, max_nr_frames=32, which seems a default value for XCP-ng. Since Xen version 4.10 max_grant_frames isn't a global config parameter issued to the hypervisor at boot time anymore. Since version 4.10 it is a parameter per domU.

              The question is, since XCP-ng has no config files per domU, how can I set domU parameter?

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              • olivierlambertO Offline
                olivierlambert Vates 🪐 Co-Founder CEO
                last edited by

                @cfischer thanks for your feedback. I might have a solution. Note this is a really complex problem in the end (interactions between xenops/xenguest and XAPI)

                I might have an patch idea to see if it works. Stay tuned.

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                • olivierlambertO Offline
                  olivierlambert Vates 🪐 Co-Founder CEO
                  last edited by

                  Due to the complicated modification, we'd like to have a support ticket created please, so we can continue to discuss those details in depth 🙂

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                  • C Offline
                    cfischer @olivierlambert
                    last edited by

                    @olivierlambert: How can I open a support ticket without buying support?

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                    • olivierlambertO Offline
                      olivierlambert Vates 🪐 Co-Founder CEO
                      last edited by

                      Here: https://xen-orchestra.com/#!/member/support

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                      • C Offline
                        cfischer @olivierlambert
                        last edited by cfischer

                        @olivierlambert: Thanks, I wasn't aware the possibility submitting tickets. Ticket created.

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                        • olivierlambertO Offline
                          olivierlambert Vates 🪐 Co-Founder CEO
                          last edited by

                          This is a free support without any commitment to answer, but it's a good way to discuss more in depth details when we can.

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                          • R Offline
                            rjt
                            last edited by

                            Does not having all the grants requested result in network slowdown?

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                            • R Offline
                              rjt @rjt
                              last edited by

                              @rjt
                              The November 2019 security, bugfix, and enhancement updates address this issue in the section "Enable increasing max_grant_frames for guests."

                              Indicates that with not enough grant frames, the guest VM will not be able to use the all the virtual NICs that it expects. Still wonder if increasing max_grant_frames would speed up existing network interfaces even when they have enough working vNICS.

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