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]). Please also add a simple test to BPF selftests using the new API. Other than that the changes look good. [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(-)
