Skip to content
  1. Dec 15, 2021
    • Andrii Nakryiko's avatar
      libbpf: Auto-bump RLIMIT_MEMLOCK if kernel needs it for BPF · e542f2c4
      Andrii Nakryiko authored
      The need to increase RLIMIT_MEMLOCK to do anything useful with BPF is
      one of the first extremely frustrating gotchas that all new BPF users go
      through and in some cases have to learn it a very hard way.
      
      Luckily, starting with upstream Linux kernel version 5.11, BPF subsystem
      dropped the dependency on memlock and uses memcg-based memory accounting
      instead. Unfortunately, detecting memcg-based BPF memory accounting is
      far from trivial (as can be evidenced by this patch), so in practice
      most BPF applications still do unconditional RLIMIT_MEMLOCK increase.
      
      As we move towards libbpf 1.0, it would be good to allow users to forget
      about RLIMIT_MEMLOCK vs memcg and let libbpf do the sensible adjustment
      automatically. This patch paves the way forward in this matter. Libbpf
      will do feature detection of memcg-based accounting, and if detected,
      will do nothing. But if the kernel is too old, just like BCC, libbpf
      will automatically increase RLIMIT_MEMLOCK on behalf of user
      application ([0]).
      
      As this is technically a breaking change, during the transition period
      applications have to opt into libbpf 1.0 mode by setting
      LIBBPF_STRICT_AUTO_RLIMIT_MEMLOCK bit when calling
      libbpf_set_strict_mode().
      
      Libbpf allows to control the exact amount of set RLIMIT_MEMLOCK limit
      with libbpf_set_memlock_rlim_max() API. Passing 0 will make libbpf do
      nothing with RLIMIT_MEMLOCK. libbpf_set_memlock_rlim_max() has to be
      called before the first bpf_prog_load(), bpf_btf_load(), or
      bpf_object__load() call, otherwise it has no effect and will return
      -EBUSY.
      
        [0] Closes: https://github.com/libbpf/libbpf/issues/369
      
      
      
      Signed-off-by: default avatarAndrii Nakryiko <andrii@kernel.org>
      Signed-off-by: default avatarDaniel Borkmann <daniel@iogearbox.net>
      Link: https://lore.kernel.org/bpf/20211214195904.1785155-2-andrii@kernel.org
      e542f2c4
  2. Dec 14, 2021
  3. Dec 13, 2021
  4. Dec 12, 2021
  5. Dec 11, 2021