[v4,bpf-next,0/5] BPF ring buffer

Implement a new BPF ring buffer, as presented at BPF virtual conference ([0]).
It presents an alternative to perf buffer, following its semantics closely,
but allowing sharing same instance of ring buffer across multiple CPUs
efficiently.

Most patches have extensive commentary explaining various aspects, so I'll
keep cover letter short. Overall structure of the patch set:
- patch #1 adds BPF ring buffer implementation to kernel and necessary
  verifier support;
- patch #2 adds libbpf consumer implementation for BPF ringbuf;
- patch #3 adds selftest, both for single BPF ring buf use case, as well as
  using it with array/hash of maps;
- patch #4 adds extensive benchmarks and provide some analysis in commit
  message, it builds upon selftests/bpf's bench runner.
- patch #5 adds most of patch #1 commit message as a doc under
  Documentation/bpf/ringbuf.rst.

Litmus tests, validating consumer/producer protocols and memory orderings,
were moved out as discussed in [1] and are going to be posted against -rcu
tree and put under Documentation/litmus-tests/bpf-rb.

  [0] https://docs.google.com/presentation/d/18ITdg77Bj6YDOH2LghxrnFxiPWe0fAqcmJY95t_qr0w
  [1] https://lkml.org/lkml/2020/5/22/1011

v3->v4:
- fix ringbuf freeing (vunmap, __free_page); verified with a trivial loop
  creating and closing ringbuf map endlessly (Daniel);

v2->v3:
- dropped unnecessary smp_wmb() (Paul);
- verifier reference type enhancement patch was dropped (Alexei);
- better verifier message for various memory access checks (Alexei);
- clarified a bit roundup_len() bit shifting (Alexei);
- converted doc to .rst (Alexei);
- fixed warning on 32-bit arches regarding tautological ring area size check.

v1->v2:
- commit()/discard()/output() accept flags (NO_WAKEUP/FORCE_WAKEUP) (Stanislav);
- bpf_ringbuf_query() added, returning available data size, ringbuf size,
  consumer/producer positions, needed to implement smarter notification policy
  (Stanislav);
- added ringbuf UAPI constants to include/uapi/linux/bpf.h (Jonathan);
- fixed sample size check, added proper ringbuf size check (Jonathan, Alexei);
- wake_up_all() is done through irq_work (Alexei);
- consistent use of smp_load_acquire/smp_store_release, no
  READ_ONCE/WRITE_ONCE (Alexei);
- added Documentation/bpf/ringbuf.txt (Stanislav);
- updated litmus test with smp_load_acquire/smp_store_release changes;
- added ring_buffer__consume() API to libbpf for busy-polling;
- ring_buffer__poll() on success returns number of records consumed;
- fixed EPOLL notifications, don't assume available data, done similarly to
  perfbuf's implementation;
- both ringbuf and perfbuf now have --rb-sampled mode, instead of
  pb-raw/pb-custom mode, updated benchmark results;
- extended ringbuf selftests to validate epoll logic/manual notification
  logic, as well as bpf_ringbuf_query().

Cc: Paul E. McKenney <paulmck@kernel.org>
Cc: Jonathan Lemon <jonathan.lemon@gmail.com>

Andrii Nakryiko (5):
  bpf: implement BPF ring buffer and verifier support for it
  libbpf: add BPF ring buffer support
  selftests/bpf: add BPF ringbuf selftests
  bpf: add BPF ringbuf and perf buffer benchmarks
  docs/bpf: add BPF ring buffer design notes

 Documentation/bpf/ringbuf.rst                 | 209 +++++++
 include/linux/bpf.h                           |  13 +
 include/linux/bpf_types.h                     |   1 +
 include/linux/bpf_verifier.h                  |   4 +
 include/uapi/linux/bpf.h                      |  84 ++-
 kernel/bpf/Makefile                           |   2 +-
 kernel/bpf/helpers.c                          |  10 +
 kernel/bpf/ringbuf.c                          | 501 ++++++++++++++++
 kernel/bpf/syscall.c                          |  12 +
 kernel/bpf/verifier.c                         | 195 ++++--
 kernel/trace/bpf_trace.c                      |  10 +
 tools/include/uapi/linux/bpf.h                |  84 ++-
 tools/lib/bpf/Build                           |   2 +-
 tools/lib/bpf/libbpf.h                        |  21 +
 tools/lib/bpf/libbpf.map                      |   5 +
 tools/lib/bpf/libbpf_probes.c                 |   5 +
 tools/lib/bpf/ringbuf.c                       | 285 +++++++++
 tools/testing/selftests/bpf/Makefile          |   5 +-
 tools/testing/selftests/bpf/bench.c           |  16 +
 .../selftests/bpf/benchs/bench_ringbufs.c     | 566 ++++++++++++++++++
 .../bpf/benchs/run_bench_ringbufs.sh          |  75 +++
 .../selftests/bpf/prog_tests/ringbuf.c        | 211 +++++++
 .../selftests/bpf/prog_tests/ringbuf_multi.c  | 102 ++++
 .../selftests/bpf/progs/perfbuf_bench.c       |  33 +
 .../selftests/bpf/progs/ringbuf_bench.c       |  60 ++
 .../selftests/bpf/progs/test_ringbuf.c        |  78 +++
 .../selftests/bpf/progs/test_ringbuf_multi.c  |  77 +++
 tools/testing/selftests/bpf/verifier/and.c    |   4 +-
 .../selftests/bpf/verifier/array_access.c     |   4 +-
 tools/testing/selftests/bpf/verifier/bounds.c |   6 +-
 tools/testing/selftests/bpf/verifier/calls.c  |   2 +-
 .../bpf/verifier/direct_value_access.c        |   4 +-
 .../bpf/verifier/helper_access_var_len.c      |   2 +-
 .../bpf/verifier/helper_value_access.c        |   6 +-
 .../selftests/bpf/verifier/value_ptr_arith.c  |   8 +-
 35 files changed, 2630 insertions(+), 72 deletions(-)
 create mode 100644 Documentation/bpf/ringbuf.rst
 create mode 100644 kernel/bpf/ringbuf.c
 create mode 100644 tools/lib/bpf/ringbuf.c
 create mode 100644 tools/testing/selftests/bpf/benchs/bench_ringbufs.c
 create mode 100755 tools/testing/selftests/bpf/benchs/run_bench_ringbufs.sh
 create mode 100644 tools/testing/selftests/bpf/prog_tests/ringbuf.c
 create mode 100644 tools/testing/selftests/bpf/prog_tests/ringbuf_multi.c
 create mode 100644 tools/testing/selftests/bpf/progs/perfbuf_bench.c
 create mode 100644 tools/testing/selftests/bpf/progs/ringbuf_bench.c
 create mode 100644 tools/testing/selftests/bpf/progs/test_ringbuf.c
 create mode 100644 tools/testing/selftests/bpf/progs/test_ringbuf_multi.c

On Fri, May 29, 2020 at 12:54:19AM -0700, Andrii Nakryiko wrote:
> Implement a new BPF ring buffer, as presented at BPF virtual conference ([0]).
> It presents an alternative to perf buffer, following its semantics closely,
> but allowing sharing same instance of ring buffer across multiple CPUs
> efficiently.
> 
> Most patches have extensive commentary explaining various aspects, so I'll
> keep cover letter short. Overall structure of the patch set:
> - patch #1 adds BPF ring buffer implementation to kernel and necessary
>   verifier support;
> - patch #2 adds libbpf consumer implementation for BPF ringbuf;
> - patch #3 adds selftest, both for single BPF ring buf use case, as well as
>   using it with array/hash of maps;
> - patch #4 adds extensive benchmarks and provide some analysis in commit
>   message, it builds upon selftests/bpf's bench runner.
> - patch #5 adds most of patch #1 commit message as a doc under
>   Documentation/bpf/ringbuf.rst.
> 
> Litmus tests, validating consumer/producer protocols and memory orderings,
> were moved out as discussed in [1] and are going to be posted against -rcu
> tree and put under Documentation/litmus-tests/bpf-rb.
> 
>   [0] https://docs.google.com/presentation/d/18ITdg77Bj6YDOH2LghxrnFxiPWe0fAqcmJY95t_qr0w
>   [1] https://lkml.org/lkml/2020/5/22/1011
> 
> v3->v4:
> - fix ringbuf freeing (vunmap, __free_page); verified with a trivial loop
>   creating and closing ringbuf map endlessly (Daniel);

Applied, thanks!