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Message-ID: <20240405223556.11142-1-andrea.righi@canonical.com>
Date: Sat, 6 Apr 2024 00:16:03 +0200
From: Andrea Righi <andrea.righi@...onical.com>
To: Andrii Nakryiko <andrii@...nel.org>,
Eduard Zingerman <eddyz87@...il.com>
Cc: Alexei Starovoitov <ast@...nel.org>,
Daniel Borkmann <daniel@...earbox.net>,
Martin KaFai Lau <martin.lau@...ux.dev>,
Song Liu <song@...nel.org>,
Yonghong Song <yonghong.song@...ux.dev>,
John Fastabend <john.fastabend@...il.com>,
KP Singh <kpsingh@...nel.org>,
Stanislav Fomichev <sdf@...gle.com>,
Hao Luo <haoluo@...gle.com>,
Jiri Olsa <jolsa@...nel.org>,
David Vernet <void@...ifault.com>,
Tejun Heo <tj@...nel.org>,
bpf@...r.kernel.org,
linux-kernel@...r.kernel.org
Subject: [PATCH v3 0/2] libbpf: API to partially consume items from ringbuffer
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@canonical.com/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
- 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(-)
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