cgroup2: podman stats is wrong

[AkihiroSuda]

Is this a BUG REPORT or FEATURE REQUEST? (leave only one on its own line)

/kind bug

Description

podman stats does not report CPU usage properly

Steps to reproduce the issue:

1. podman run -it --rm --cpus 1.0 --runtime=/usr/local/bin/crun alpine sh -c "apk add --no-cache stress-ng && stress-ng -c 0
2. podman stats

Describe the results you received:

CPU % won't reach more than 10%

Describe the results you expected:

Should be about 100%.

systemd-cgtop can report it properly.

Additional information you deem important (e.g. issue happens only occasionally):

Output of podman version:

Version:            1.6.3-dev
RemoteAPI Version:  1
Go Version:         go1.13.3
Git Commit:         2dae2577ccbeef502a8783c892a6c9e346153532
Built:              Fri Nov  1 14:48:38 2019
OS/Arch:            linux/amd64

Output of podman info --debug:

debug:
  compiler: gc
  git commit: 2dae2577ccbeef502a8783c892a6c9e346153532
  go version: go1.13.3
  podman version: 1.6.3-dev
host:
  BuildahVersion: 1.11.4
  CgroupVersion: v2
  Conmon:
    package: Unknown
    path: /usr/local/bin/conmon
    version: 'conmon version 2.0.3-dev, commit: bc758d8bd98a29ac3aa4f62a886575bfec0e39a1'
  Distribution:
    distribution: ubuntu
    version: "19.10"
  MemFree: 3149606912
  MemTotal: 8318803968
  OCIRuntime:
    name: crun
    package: Unknown
    path: /usr/local/bin/crun
    version: |-
      crun version 0.10.4
      spec: 1.0.0
      +SYSTEMD +SELINUX +APPARMOR +CAP +SECCOMP +EBPF +YAJL
  SwapFree: 2147479552
  SwapTotal: 2147479552
  arch: amd64
  cpus: 2
  eventlogger: journald
  hostname: suda-ws01
  kernel: 5.3.0-19-generic
  os: linux
  rootless: false
  uptime: 8h 12m 2.71s (Approximately 0.33 days)
registries:
  blocked: null
  insecure: null
  search:
  - docker.io
store:
  ConfigFile: /etc/containers/storage.conf
  ContainerStore:
    number: 15
  GraphDriverName: overlay
  GraphOptions: {}
  GraphRoot: /var/lib/containers/storage
  GraphStatus:
    Backing Filesystem: extfs
    Native Overlay Diff: "true"
    Supports d_type: "true"
    Using metacopy: "false"
  ImageStore:
    number: 21
  RunRoot: /var/run/containers/storage
  VolumePath: /var/lib/containers/storage/volumes

[rhatdan]

@AkihiroSuda Do you want to open a PR to fix this?

[giuseppe]

I see the same issue on cgroups v1.

I've opened a PR, tested both with cgroups v1 and cgroups v2: #4423