mainlining shenanigans
e255d32739
Andrii Nakryiko says: ==================== 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(). ==================== Signed-off-by: Daniel Borkmann <daniel@iogearbox.net> |
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Linux kernel
============
There are several guides for kernel developers and users. These guides can
be rendered in a number of formats, like HTML and PDF. Please read
Documentation/admin-guide/README.rst first.
In order to build the documentation, use ``make htmldocs`` or
``make pdfdocs``. The formatted documentation can also be read online at:
https://www.kernel.org/doc/html/latest/
There are various text files in the Documentation/ subdirectory,
several of them using the Restructured Text markup notation.
Please read the Documentation/process/changes.rst file, as it contains the
requirements for building and running the kernel, and information about
the problems which may result by upgrading your kernel.