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    Alert: Control Domain Memory Usage

    Scheduled Pinned Locked Moved Solved Compute
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    • delafD Offline
      delaf @delaf
      last edited by

      FYI: I confirm that on the server running the alt kernel I do not have anymore the memleak problem :

      # yum list installed | grep kernel
      kernel.x86_64                   4.19.19-6.0.12.1.1.kmemleak.xcpng8.1
      kernel-alt.x86_64               4.19.108-3.xcpng8.1         @xcp-ng-base
      # uname -a
      Linux bb0266.aquaray.com 4.19.108 #1 SMP Mon Mar 23 15:04:05 CET 2020 x86_64 x86_64 x86_64 GNU/Linux
      #
      

      Memory graph from this server :
      Screen Shot 2020-11-20 at 12.14.54.png

      Obviously, the alt-kernel has been installed ~2020-11-13.

      On the server running the memleak kernel (since yesterday) :
      Screen Shot 2020-11-20 at 12.16.21.png

      olivierlambertO 1 Reply Last reply Reply Quote 0
      • olivierlambertO Online
        olivierlambert Vates 🪐 Co-Founder CEO @delaf
        last edited by

        @delaf Weird but interesting!

        R 1 Reply Last reply Reply Quote 0
        • R Offline
          r1 XCP-ng Team @olivierlambert
          last edited by

          @olivierlambert @delaf what we know from kmemleak so far is that it will only scan and report unreferenced objects. If any kernel module / kernel itself is still holding(referencing) the memory then it may not show up. We are evaluating other options to find this.

          kernel-alt is more related to upstream, so either this issue is known and fixed in upstream or it might have been introduced from kernel updates.

          The oldest kernel available is 4.19.19-6.0.10.1.xcpng8.1, is it possible to install it and see if the issue repeats?

          delafD 1 Reply Last reply Reply Quote 0
          • stormiS Offline
            stormi Vates 🪐 XCP-ng Team
            last edited by

            kernel-alt also means that all the drivers used are buillt-in, no those from the driver packages that take precedence over the built-ins when running the main kernel.

            R 1 Reply Last reply Reply Quote 0
            • R Offline
              r1 XCP-ng Team @stormi
              last edited by r1

              Yes, all drivers are stock kernel modules for kernel-alt. It would be interesting to see the behavior by disabling updates and override. I think we can try both. 1st check if the downgraded kernel shows same symptoms and then disabling update drivers.

              1 Reply Last reply Reply Quote 0
              • stormiS Offline
                stormi Vates 🪐 XCP-ng Team
                last edited by stormi

                Ok, so now we know for sure that it's related to the kernel or one of the drivers.

                Let me summarize all the tests that users affected by the issue can do to help find what causes it:

                • Test with kmemleak, hoping that it may be able to detect something. No luck for now for @delaf who tried.
                • Test with the oldest kernel (4.19.19-6.0.10.1.xcpng8.1). I doubt it will yield results, but that would allow to be sure. If it does yield results, then it will allow to search towards a specific patch.
                • With the current kernel, give priority to built-in drivers. If this gives good results, this will mean that the leak is in one of the drivers that are provided through driver RPMs. Two ways:
                  • A bit riskier but we'd still be interested in the results: disable them all so that only built-in kernel drivers are used. For this, edit /etc/modprobe.d/dist.conf and change search override updates extra built-in weak-updates into search extra built-in weak-updates override updates, then run depmod -a and reboot. Don't forget to restore the original contents after the tests.
                  • Another way, that allows to select specific drivers one by one:
                    • Identify a few drivers that you want to check in the output of lsmod. For example ixgbe.
                    • Find where the currently used driver is on the filesystem: modinfo ixgbe | head -n 1
                    • If the path contains "/updates/", it's not a kernel built-in. Rename the file to name_of_file.save. depmod -a. reboot. The kernel will then use its built-in driver.
                    • If nothing changes, restore the file and try another.

                I also intend to build a new ixgbe driver, just in case we're lucky and it's the culprit, since every affected user uses it.

                delafD 1 Reply Last reply Reply Quote 0
                • delafD Offline
                  delaf @r1
                  last edited by

                  @r1 I do not manage to install the old kernel. Any idea?

                  # yum downgrade "kernel == 4.19.19-6.0.10.1.xcpng8.1"
                  Loaded plugins: fastestmirror
                  Loading mirror speeds from cached hostfile
                  Excluding mirror: updates.xcp-ng.org
                   * xcp-ng-base: mirrors.xcp-ng.org
                  Excluding mirror: updates.xcp-ng.org
                   * xcp-ng-updates: mirrors.xcp-ng.org
                  Resolving Dependencies
                  --> Running transaction check
                  ---> Package kernel.x86_64 0:4.19.19-6.0.10.1.xcpng8.1 will be a downgrade
                  ---> Package kernel.x86_64 0:4.19.19-6.0.12.1.xcpng8.1 will be erased
                  --> Finished Dependency Resolution
                  Error: Trying to remove "kernel", which is protected
                  
                  1 Reply Last reply Reply Quote 0
                  • DanpD Offline
                    Danp Pro Support Team
                    last edited by

                    @delaf I ran into the same thing recently. See solution below --

                    https://xcp-ng.org/forum/post/33291

                    delafD 1 Reply Last reply Reply Quote 1
                    • delafD Offline
                      delaf @stormi
                      last edited by

                      @stormi I have a server with only search extra built-in weak-updates override updates. We will see if it is better.

                      1 Reply Last reply Reply Quote 1
                      • delafD Offline
                        delaf @Danp
                        last edited by

                        @danp Thank you. I have downgraded one server.

                        @stormi So i have :

                        • one server with 4.19.19-6.0.10.1.xcpng8.1
                        • one server with kmemleak kernel
                        • one server with search extra built-in weak-updates override updates
                        delafD 1 Reply Last reply Reply Quote 1
                        • delafD Offline
                          delaf @delaf
                          last edited by

                          @stormi @r1
                          Four days later, I get:

                          • one server (266) with alt-kernel: still no problem
                          • one server (268) with 4.19.19-6.0.10.1.xcpng8.1: no more problem!
                          • one server (272) with kmemleak kernel: no memleak detected, but the problem is present
                          • one server (273) with search extra built-in weak-updates override updates: problem still present
                          R 1 Reply Last reply Reply Quote 1
                          • stormiS Offline
                            stormi Vates 🪐 XCP-ng Team
                            last edited by

                            @delaf Excellent news, especially if you can replicate on another host to be sure.

                            This thread is older than kernel-4.19.19-6.0.10.1.xcpng8.1 (especially in @dave's case), but it wouldn't be unlikely that several distinct memory leak causes exist.

                            1 Reply Last reply Reply Quote 0
                            • R Offline
                              r1 XCP-ng Team @delaf
                              last edited by

                              @delaf said in Alert: Control Domain Memory Usage:

                              one server (268) with 4.19.19-6.0.10.1.xcpng8.1: no more problem!

                              Yeah, we need to be sure that this is a stable kernel and somewhere after this, the memory leak seems to have introduced.

                              1 Reply Last reply Reply Quote 0
                              • daveD Offline
                                dave
                                last edited by

                                I currently have:

                                top - 13:35:31 up 59 days, 17:11,  1 user,  load average: 0.43, 0.36, 0.34
                                Tasks: 646 total,   1 running, 436 sleeping,   0 stopped,   0 zombie
                                %Cpu(s):  0.8 us,  1.1 sy,  0.0 ni, 97.5 id,  0.3 wa,  0.0 hi,  0.1 si,  0.2 st
                                KiB Mem : 12205936 total,   149152 free, 10627080 used,  1429704 buff/cache
                                KiB Swap:  1048572 total,  1048572 free,        0 used.  1153360 avail Mem
                                
                                
                                top - 13:35:54 up 35 days, 17:29,  1 user,  load average: 0.54, 0.73, 0.77
                                Tasks: 489 total,   1 running, 324 sleeping,   0 stopped,   0 zombie
                                %Cpu(s):  3.5 us,  3.4 sy,  0.0 ni, 92.7 id,  0.0 wa,  0.0 hi,  0.0 si,  0.4 st
                                KiB Mem : 12207996 total,   155084 free,  9388032 used,  2664880 buff/cache
                                KiB Swap:  1048572 total,  1048572 free,        0 used.  2394220 avail Mem
                                
                                

                                both with:

                                # uname -a
                                Linux xs01 4.19.0+1 #1 SMP Thu Jun 11 16:18:33 CEST 2020 x86_64 x86_64 x86_64 GNU/Linux
                                # yum list installed | grep kernel
                                kernel.x86_64                   4.19.19-6.0.11.1.xcpng8.1   @xcp-ng-updates
                                
                                

                                shall i test something?

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                                • U Offline
                                  umbradark
                                  last edited by

                                  I have a set of hosts on kernel-4.19.19-6.0.11.1.xcpng8.1 and I believe I'm hitting this as well. The OOM seems to kill openvswitch, which takes the host offline and in most cases, the VMs as well.

                                  1 Reply Last reply Reply Quote 0
                                  • stormiS Offline
                                    stormi Vates 🪐 XCP-ng Team
                                    last edited by

                                    So, the difference between 4.19.19-6.0.10.1.xcpng8.1 and 4.19.19-6.0.11.1.xcpng8.1 is two patches meant to reduce the performance overhead of the CROSSTalk vulnerability mitigations.

                                    So, assuming from @delaf's test results that one of those patches introduced the memory leak, I have built

                                    Now here are the tests that you can do:

                                    • Reproduce @delaf's findings by running kernel-4.19.19-6.0.10.1.xcpng8.1: no more memory leaks?
                                    • Test this kernel I built with patch 53 disabled: https://nextcloud.vates.fr/index.php/s/YXWCSEwo8SWkfAZ
                                    • Test this kernel I built with patch 62 disabled: https://nextcloud.vates.fr/index.php/s/arj5YfdrkjMKbBy

                                    If one of the patches is the cause of the memory leak, then one of the last two should still cause a memory leak and the other one not.

                                    delafD 1 Reply Last reply Reply Quote 0
                                    • delafD Offline
                                      delaf @stormi
                                      last edited by delaf

                                      @stormi I have installed the two kernels

                                      272 ~]# yum list installed kernel | grep kernel
                                      kernel.x86_64                   4.19.19-6.0.11.1.0.1.patch53disabled.xcpng8.1
                                      
                                      273 ~]# yum list installed kernel | grep kernel
                                      kernel.x86_64                   4.19.19-6.0.11.1.0.1.patch62disabled.xcpng8.1
                                      

                                      I have removed the modification in /etc/modprobe.d/dist.conf on server 273.

                                      We have to wait a little bit now 😉

                                      1 Reply Last reply Reply Quote 1
                                      • stormiS Offline
                                        stormi Vates 🪐 XCP-ng Team
                                        last edited by

                                        FYI, the kernel with kmemleak support did detect something for a user who has a support ticket related to dom0 memory usage.

                                        delafD 1 Reply Last reply Reply Quote 0
                                        • delafD Offline
                                          delaf @stormi
                                          last edited by

                                          @stormi For the kernel-4.19.19-6.0.10.1.xcpng8.1 test, i'm not sure it solve the problem because I get a small memory increase. We have to wait a bit more 😕

                                          delafD 1 Reply Last reply Reply Quote 1
                                          • delafD Offline
                                            delaf @delaf
                                            last edited by olivierlambert

                                            @stormi

                                            • server 266 with alt-kernel: still no problem.
                                              Screen Shot 2020-12-02 at 10.08.47.png

                                            • server 268 with 4.19.19-6.0.10.1.xcpng8.1: the problem has begun some days ago after some stable days.
                                              Screen Shot 2020-12-02 at 10.03.57.png

                                            • server 272 with 4.19.19-6.0.11.1.0.1.patch53disabled.xcpng8.1:
                                              Screen Shot 2020-12-02 at 10.05.47.png )

                                            • server 273 with 4.19.19-6.0.11.1.0.1.patch62disabled.xcpng8.1:
                                              Screen Shot 2020-12-02 at 10.05.50.png

                                            It seems that 4.19.19-6.0.11.1.0.1.patch62disabled.xcpng8.1 is more stable than 4.19.19-6.0.11.1.0.1.patch53disabled.xcpng8.1. But it is a but early to be sure.

                                            delafD 1 Reply Last reply Reply Quote 1
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