Question to gitlab-runner default cpu usage

GitLab Community,

As I’ve check your documentation (Advanced configuration | GitLab) for gitlab runner parameters and configuration I can’t see, what is the default limit for runners in cpu-usage?

How many cores use a gitlab-runner by default from my CPU?

For example a configuration (config.toml) from one of our build servers (runners):

concurrent = 4
check_interval = 5
log_level = "warning"
log_format = "runner"

[session_server]
  session_timeout = 1800

[[runners]]
  name = "example-runner"
  url = "https://git.foo.bar/"
  token = "XXXX"
  executor = "docker"
  [runners.custom_build_dir]
  [runners.cache]
    [runners.cache.s3]
    [runners.cache.gcs]
    [runners.cache.azure]
  [runners.docker]
    tls_verify = false
    image = "alpine:latest"
    privileged = false
    disable_entrypoint_overwrite = false
    oom_kill_disable = false
    disable_cache = false
    volumes = ["/mnt/container/cache/example-runner:/cache:rw", "/var/run/docker.sock:/var/run/docker.sock"]
    pull_policy = ["if-not-present"]
    shm_size = 0