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    [XCP-ng 8] max_grant_frames reached

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    • C Offline
      cfischer
      last edited by olivierlambert

      Hello,

      got the following while started a VyOS router:

      [    2.072983] xen:grant_table: xen/grant-table: max_grant_frames reached cur=32 extra=1 limit=32 gnttab_free_count=191 req_entries=65
      [    2.072985] xen_netfront: can't alloc rx grant refs
      [    2.092487] vif vif-7: only created 3 queues
      

      Do you know who is limiting domU to 32 pages while dom0 has 64 per default?

      11:14 xs1 ~]# xen-diag gnttab_query_size 0
      domid=0: nr_frames=1, max_nr_frames=64
      [11:14 xs1 ~]# xen-diag gnttab_query_size 1
      domid=1: nr_frames=32, max_nr_frames=32
      

      Thanks
      Christian

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

        What kind of template are you using? Other media install?

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        • C Offline
          cfischer
          last edited by

          Yes, Other media

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          • C Offline
            cfischer @olivierlambert
            last edited by

            @olivierlambert: I can't find a restriction of this kind in the template.

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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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