Fix cgroup v2 swap-only memory metrics for KIND

[AkshatDudeja77]

This change fixes reporting of swap-only memory metrics for cgroup v2.

Previously, swap usage was either missing or incorrectly derived. This update
adds proper parsing and exposure of swap-only usage so that metrics such as
container_memory_swap and related fields reflect actual cgroup v2 behavior.

Tested locally on cgroup v2 (WSL2) and verified metrics via /metrics endpoint.

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[AkshatDudeja77]

I’ve signed the Google CLA. Could you please recheck?

[SergeyKanzhelev]

/cc @ajaysundark

[dims]

@AkshatDudeja77 the PR is not complete. just adding a file in vendor/ is not going to help from what i can tell.

[ajaysundark]

The description is misleading. it is not that cgroupv2 swap/stats collection is not working, but it is not working for "kind".

The file added in this PR is from opencontainers/cgroups which is the module used by cadvisor for stats collection. And from what I can see here: https://github.com/opencontainers/cgroups/blob/e0c56cb31dcb3cb2b3d1554b20dd01ced32e2a2b/fs2/memory.go#L115-L119 cgroupv2 swap collection is correctly handled.

I dont see any code changes in this file, it seems to be just a plain import. did you miss to add your changes in the cadvisor itself?

[ajaysundark]

/retitle Fix cgroup v2 swap-only memory metrics for KIND

[AkshatDudeja77]

Thanks for the clarification. I agree that this issue is specific to KIND. I’ve updated the PR title accordingly and will add the missing cAdvisor-side changes.

[AkshatDudeja77]

This PR fixes incorrect swap reporting under cgroup v2.

Previously, cAdvisor derived swap as SwapUsage - MemoryUsage, which is incorrect for cgroup v2.

The fix ensures swap metrics are sourced from cgroup v2 swap-only accounting, aligning container stats with kernel semantics and Prometheus metrics output.