On Fri, Apr 05, 2024 at 04:16:34PM -0700, Andrii Nakryiko wrote: > On Fri, Apr 5, 2024 at 3:36 PM Andrea Righi <andrea.righi@xxxxxxxxxxxxx> wrote: > > > > Introduce ring__consume_n() and ring_buffer__consume_n() API to > > partially consume items from one (or more) ringbuffer(s). > > > > This can be useful, for example, to consume just a single item or when > > we need to copy multiple items to a limited user-space buffer from the > > ringbuffer callback. > > > > Practical example (where this API can be used): > > https://github.com/sched-ext/scx/blob/b7c06b9ed9f72cad83c31e39e9c4e2cfd8683a55/rust/scx_rustland_core/src/bpf.rs#L217 > > > > See also: > > https://lore.kernel.org/lkml/20240310154726.734289-1-andrea.righi@xxxxxxxxxxxxx/T/#u > > > > [ Note: I haven't implemented the special case of n == 0 as "no limit", > > because we still need to add a bunch of extra checks for INT_MAX, making > > the code less readable and, from a performance perspective, it seems > > that we may get more downsides than benefits, but I can try to look more > > at this if you think it's worth it ] > > > > v3: > > - rename ring__consume_max() -> ring__consume_n() and > > ring_buffer__consume_max() -> ring_buffer__consume_n() > > - add new API to a new 1.5.0 cycle > > You also need to update Makefile, CI is failing right now ([0]). Yep, I wasn't sure if should have bumped up the version as well (in libbpf_version.h). I'll add that. > > Please also add a simple test to BPF selftests using the new API. > Other than that the changes look good. Ok, will add a selftest. Thanks, -Andrea > > [0] https://github.com/kernel-patches/bpf/actions/runs/8576515495/job/23507610313#step:11:73 > > pw-bot: cr > > > - fixed minor nits / comments > > > > v2: > > - introduce a new API instead of changing the callback's retcode > > behavior > > > > Andrea Righi (2): > > libbpf: ringbuf: allow to consume up to a certain amount of items > > libbpf: Add ring__consume_n / ring_buffer__consume_n > > > > tools/lib/bpf/libbpf.h | 12 ++++++++++ > > tools/lib/bpf/libbpf.map | 6 +++++ > > tools/lib/bpf/ringbuf.c | 59 ++++++++++++++++++++++++++++++++++++++++-------- > > 3 files changed, 67 insertions(+), 10 deletions(-)
