Generate correct output on NumCPU() when using cgroups2

[nickorlow]

Updates the NumCPU() function in pkg/util/runtime/cpu_linux.go to work with cgroups2.

What this PR does / why we need it:

Change is required for proper functionality with cgroups2.

Types of changes

• [x] Bug fix (non-breaking change which fixes an issue)
• [x] New feature (non-breaking change which adds functionality)
• [ ] CVE Report (Scanner found CVE and adding report)
• [ ] Breaking change (fix or feature that would cause existing functionality to change)
• [ ] Documentation only

Which issue/s this PR fixes

Fixes #9665

How Has This Been Tested?

Generated example files that were within the [cgroups2 spec](https://docs.kernel.org/admin-guide/cgroup-v2.html and tested our code to ensure it returned the correct outputs for each case.

Checklist:

• [ ] My change requires a change to the documentation.
• [ ] I have updated the documentation accordingly.
• [x] I've read the CONTRIBUTION guide
• [ ] I have added unit and/or e2e tests to cover my changes.
• [ ] All new and existing tests passed.
• [ ] Added Release Notes.

Does my pull request need a release note?

Added support for detecting CPU count properly when using cgroups2

[linux-foundation-easycla[bot]]

The committers listed above are authorized under a signed CLA.

• :white_check_mark: login: nickorlow / name: Nicholas Orlowsky (8f86603dbdc316293425dc22bf82ce4aca4b7d3c, a9f9793a1fbe269660c70ef9ea33c03f541cc689, 3814e1f01fbfebe4c8c9f88e57cd424a56578537, be6f1d54c75af5c7ce6db646fe99deb0f77b6570, 475adf734ad9f1d85ece1d344a2b2636de7b4fa4, c5dad5e46116382ef8ec02a648e9c48d0ef1ea19, 0a01f555d19a9456a9924ce19e5ad51808805e91, 6d96e111c8e15081c36bf0448745cb3eb73b1cb4, e4a11295abc4bfd72990ebf7d7b25b6ecfe17cca, 63fb4c65126347dd7d578bfaf699d0843852708c, c23cc0c33877eab2865fa21240318305cfadaf44, aa9a87621742343c8188cc7f89be234e9f956e8f, f35dae9b1117a6e0da532702bb4978ea8547175f, 3714c2c426885e8b4730cefc6b04d3d997102bec, 221e85f6f2e11455cdeeb5b2d4cfd93b51b575c1, a8028a576f3174e9063f55ccc96c5345bf0357b1, b270b4a8bf108dd210b209b1babb61a6bf5b840d, 0f4d054c0766cacc3e4fde487f8ac0439f1cd0ac, ad1fb03f002d6378a9293e08c2c9163030f9287c, dad8086cb2b992c37736e2645aaabd0a36129735, fddf4e034c0d766a4815247b414cbd71a1869456, 3ae35a045dc0d103c6d6511ffa516ebddb11ac14, 30dc62987192e6a6ca797c403148549b86bd30f7, a080ea1f29bf1b48b5cfe8cdda2f0278c185f487, 3a64d7402c1869c4a3dc60056b797d27f9765beb, 7f6472617bf086712d995418e2e4df98e2ee4682, 405a5aa44c828d151c62d914e68cd39954370152, 8621dfc66dbe9c84b4e0bcae8916f44ef4d2620a, 9e79a360204a29613061e0055315538696287788, 7c4ac85a48c8d55417f33648dab87641a7105b7e, ac0f6fcd398065bd2ce54c655480a7ed32526127)
• :white_check_mark: login: sridharnandigam / name: Sridhar Nandigam (165d0573618c5bcd42962de100b75666c6fe15b3)

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[longwuyuan]

Hi @nickorlow ,

Thanks for this.

Please explore contributing tests for this. Particularly e2e tests.

regards

[longwuyuan]

/triage accepted /kind bug

[nickorlow]

Hi @nickorlow ,

Thanks for this.

Please explore contributing tests for this. Particularly e2e tests.

regards

Should we include the tests in this PR or make a separate one?

[longwuyuan]

I think that the change and the e2e-test in this PR will help feedback. thanks

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The committers listed above are authorized under a signed CLA.

• :white_check_mark: login: nickorlow / name: Nicholas Orlowsky (e4a11295abc4bfd72990ebf7d7b25b6ecfe17cca, 221e85f6f2e11455cdeeb5b2d4cfd93b51b575c1, 3ae35a045dc0d103c6d6511ffa516ebddb11ac14, 7f6472617bf086712d995418e2e4df98e2ee4682, a080ea1f29bf1b48b5cfe8cdda2f0278c185f487, f35dae9b1117a6e0da532702bb4978ea8547175f, dad8086cb2b992c37736e2645aaabd0a36129735, 7c4ac85a48c8d55417f33648dab87641a7105b7e)
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[Preetham777]

Hi @nickorlow I used the code changes you did and patched the same files. Apparently, the code seems to be not correct and usage of a function FindCgroupMountpoint is forbidden for the cgroups v2 and thus leads to runtime.NumCPU() always.

When tested in GKE 1.26 here was the error from the code: not implemented for cgroup v2 unified hierarchy

[nginx@pree-new-ic-gke-pree-ingress-96c6776d8-w66ch nginx-config]$ uname -a
Linux pree-new-ic-gke-pree-ingress-96c6776d8-w66ch 5.15.89+ #1 SMP Sat Mar 18 09:27:02 UTC 2023 x86_64 x86_64 x86_64 GNU/Linux

----


[nginx@pree-new-ic-gke-pree-ingress-96c6776d8-w66ch nginx-config]$ ls /sys/fs/cgroup/
cgroup.controllers        cpu.max                   hugetlb.1GB.events        io.pressure               memory.stat
cgroup.events             cpu.max.burst             hugetlb.1GB.events.local  io.stat                   memory.swap.current
cgroup.freeze             cpu.pressure              hugetlb.1GB.max           memory.current            memory.swap.events
cgroup.kill               cpu.stat                  hugetlb.1GB.rsvd.current  memory.events             memory.swap.high
cgroup.max.depth          cpu.weight                hugetlb.1GB.rsvd.max      memory.events.local       memory.swap.max
cgroup.max.descendants    cpu.weight.nice           hugetlb.2MB.current       memory.high               pids.current
cgroup.procs              cpuset.cpus               hugetlb.2MB.events        memory.low                pids.events
cgroup.stat               cpuset.cpus.effective     hugetlb.2MB.events.local  memory.max                pids.max
cgroup.subtree_control    cpuset.cpus.partition     hugetlb.2MB.max           memory.min                rdma.current
cgroup.threads            cpuset.mems               hugetlb.2MB.rsvd.current  memory.numa_stat          rdma.max
cgroup.type               cpuset.mems.effective     hugetlb.2MB.rsvd.max      memory.oom.group
cpu.idle                  hugetlb.1GB.current       io.max                    memory.pressure

References :

• https://github.com/opencontainers/runc/blob/v1.1.5/libcontainer/cgroups/v1_utils.go#L18
• https://github.com/opencontainers/runc/commit/142d0f2d5d75a2848beefb373708dab78f6d9329

[nickorlow]

Hey @Preetham777 ill look into this today. Thank you for finding it!

[nickorlow]

@Preetham777 just pushed a fix. Have yet to test it (writing the e2e tests for it right now) but I believe this should resolve your issue.

[strongjz]

i dont think our kind e2e tests use cgroup v2 so none of our e2e tests will hit the new code paths.

How are we certain this will work on cgroup v2 clusters.

Also looks like this is a merge conflict in the e2e files. /hold

[nickorlow]

i dont think our kind e2e tests use cgroup v2 so none of our e2e tests will hit the new code paths.

How are we certain this will work on cgroup v2 clusters.

Also looks like this is a merge conflict in the e2e files. /hold

Our plan for the e2e tests was to create the cgroups files that NumCPU reads from and then run the NumCPU function to check that it's value is consistent with what we expect. Does this seem like a good approach?

We have tested the code by creating a separate standalone program with the same code from the cpu_linux.go fille and running it on a cgroups2 system. We have not yet built and deployed this on a cluster.

I've removed some of our e2e progress as it wasn't finished yet.

[LeMyst]

Any news about this PR?

[nickorlow]

Any news about this PR?

Just fixed the formatting issue. Would appreciate input on what to do with the e2e tests regarding my last comment (or if we should write any at all)

[MKruger777]

Any news on this PR? bumping into the same issue :-(

[tao12345666333]

Sorry for the delay. Let me take a look.

/assign

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[nickorlow]

Added e2e tests. I made it so that the cgroups files are created during the test so they're not somewhere else in the test config and also we can test the correct output on v1/v2 without requiring the kind cluster be re-created with different cgroup settings.

[tao12345666333]

Thank you for your contribution

[LeMyst]

LGTM for the moment

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[runephilosof-karnovgroup]

@nickorlow @tao12345666333 Looks like this is stalled/forgotten?

[nickorlow]

@nickorlow @tao12345666333 Looks like this is stalled/forgotten?

I think so.. anything more I need to do to have this merged? I believe all requested changes have been made

[LeMyst]

Any news?

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[scenusa-bd]

Any plans to have this merged? Thanks!

[tao12345666333]

@nickorlow Sorry for the long long delay, could you please resolve the conflicts and make a rebase? Then we can move forward, thank you!

[divigarg]

@nickorlow , can we get this through, please? thank you :)