BPF programs statistics

This page shows you how to monitor bpf programs statistics.

Concept

The BPF subsystem provides performance data for each loaded program and tetragon exports that in metrics or display that in terminal in top like tool.

In terminal

The tetra command allows to display loaded BPF programs in terminal with:

tetra debug progs

The default output shows tetragon programs only and looks like:

2024-10-31 11:12:45.94715546 +0000 UTC m=+8.038098448

Ovh(%)  Id      Cnt     Time    Name                            Pin
  0.00  22201   0       0       event_execve                    /sys/fs/bpf/tetragon/__base__/event_execve/prog
  0.00  22198   0       0       event_exit_acct_process         /sys/fs/bpf/tetragon/__base__/event_exit/prog
  0.00  22200   0       0       event_wake_up_new_task          /sys/fs/bpf/tetragon/__base__/kprobe_pid_clear/prog
  0.00  22207   0       0       tg_cgroup_rmdir                 /sys/fs/bpf/tetragon/__base__/tg_cgroup_rmdir/prog
  0.00  22206   0       0       tg_kp_bprm_committing_creds     /sys/fs/bpf/tetragon/__base__/tg_kp_bprm_committing_creds/prog
  0.00  22221   0       0       generic_kprobe_event            /sys/fs/bpf/tetragon/syswritefollowfdpsswd/generic_kprobe/__x64_sys_close/prog
  0.00  22225   0       0       generic_kprobe_event            /sys/fs/bpf/tetragon/syswritefollowfdpsswd/generic_kprobe/__x64_sys_write/prog
  0.00  22211   0       0       generic_kprobe_event            /sys/fs/bpf/tetragon/syswritefollowfdpsswd/generic_kprobe/fd_install/prog

The fields have following meaning:

• Ovh is system wide overhead of the BPF program
• Id is global BPF ID of the program (as shown by bpftool prog)
• Cnt is count with number of BPF program executions
• Time is sum of the time of all BPF program executions
• Pin is BPF program pin path in bpfffs

It’s possible to display all BPF programs with --all:

tetra debug progs --all

That has following output:

2024-10-31 11:19:37.720137195 +0000 UTC m=+7.165535117

Ovh(%)  Id      Cnt     Time    Name            Pin
  0.00  159     2       82620   event_execve    -
  0.00  171     68      18564   iter            -
  0.00  158     2       10170   event_wake_up_n -
  0.00  164     2       4254    tg_kp_bprm_comm -
  0.00  157     2       3868    event_exit_acct -
  0.00  97      2       1680                    -
  0.00  35      2       1442                    -
  0.00  83      0       0       sd_devices      -
  0.00  9       0       0                       -
  0.00  7       0       0                       -
  0.00  8       0       0                       -
  0.00  87      0       0       sd_devices      -
...

Above commands should run properly on top of the tetragon sources. At the moment to run it properly under Kubernetes you need to specify extra directory flags:

kubectl exec -ti -n kube-system tetragon-66rk4 -c tetragon -- tetra debug progs --bpf-dir /run/cilium/bpffs/tetragon/ --all --bpf-lib /var/lib/tetragon/

Note that there are other options to customize the behaviour:

tetra debug progs --help

Retrieve information about BPF programs on the host.

Examples:
- tetragon BPF programs top style
  # tetra debug progs
- all BPF programs top style
  # tetra debug progs --all
- one shot mode (displays one interval data)
  # tetra debug progs --once
- change interval to 10 seconds
  # tetra debug progs  --timeout 10
- change interval to 10 seconds in one shot mode
  # tetra debug progs --once --timeout 10

Usage:
  tetra debug progs [flags]

Aliases:
  progs, top

Flags:
      --all              Get all programs
      --bpf-dir string   Location of bpffs tetragon directory (default "/sys/fs/bpf/tetragon")
      --bpf-lib string   Location of Tetragon libs (btf and bpf files) (default "bpf/objs/")
  -h, --help             help for progs
      --no-clear         Do not clear screen between rounds
      --once             Run in one shot mode
      --timeout int      Interval in seconds (delay in one shot mode) (default 1)

Metrics

The BPF subsystem provides performance data for each loaded program and tetragon exports that in metrics.

For each loaded BPF program we get:

• run count which counts how many times the BPF program was executed
• run time which sums the time BPF program spent in all its executions

Hence for each loaded BPF program we export 2 related metrics:

• tetragon_overhead_time_program_total[namespace,policy,sensor,attach]
• tetragon_overhead_cnt_program_total[namespace,policy,sensor,attach]

Each loaded program is identified by labels:

• namespace is policy Kubernetes namespace
• policy is policy name
• sensor is sensor name
• attach is program attachment name

If we have generic_kprobe sensor attached on __x64_sys_close kernel function under syswritefollowfdpsswd policy, the related metrics will look like:

tetragon_overhead_program_runs_total{attach="__x64_sys_close",policy="syswritefollowfdpsswd",policy_namespace="",sensor="generic_kprobe"} 15894
tetragon_overhead_program_seconds_total{attach="__x64_sys_close",policy="syswritefollowfdpsswd",policy_namespace="",sensor="generic_kprobe"} 1.03908217e+08

Limitations

Note that the BPF programs statistics are not enabled by default, because they introduce extra overhead, so it’s necessary to enable them manually.

• Either with sysctl:

  sysctl kernel.bpf_stats_enabled=1
  

  and make sure you disable the stats when it’s no longer needed:

  sysctl kernel.bpf_stats_enabled=0
  

• Or with following tetra command:

  tetra debug enable-stats
  ^C
  

  where the stats are enabled as long as the command is running (sleeping really).