[PATCH] libbpf: Expose API to consume one ring at a time

Adam Sindelar
2023-07-25T16:37:46Z

We already provide ring_buffer__epoll_fd to enable use of external
polling systems. However, the only API available to consume the ring
buffer is ring_buffer__consume, which always checks all rings. When
polling for many events, this can be wasteful.

Signed-off-by: Adam Sindelar <adam@wowsignal.io>
---
tools/lib/bpf/libbpf.h | 1 +
tools/lib/bpf/ringbuf.c | 15 +++++++++++++++
2 files changed, 16 insertions(+)

diff --git a/tools/lib/bpf/libbpf.h b/tools/lib/bpf/libbpf.h
index 55b97b2087540..20ccc65eb3f9d 100644
--- a/tools/lib/bpf/libbpf.h
+++ b/tools/lib/bpf/libbpf.h
@@ -1195,6 +1195,7 @@ LIBBPF_API int ring_buffer__add(struct ring_buffer *rb, int map_fd,
ring_buffer_sample_fn sample_cb, void *ctx);
LIBBPF_API int ring_buffer__poll(struct ring_buffer *rb, int timeout_ms);
LIBBPF_API int ring_buffer__consume(struct ring_buffer *rb);
+LIBBPF_API int ring_buffer__consume_ring(struct ring_buffer *rb, uint32_t ring_id);
LIBBPF_API int ring_buffer__epoll_fd(const struct ring_buffer *rb);

struct user_ring_buffer_opts {
diff --git a/tools/lib/bpf/ringbuf.c b/tools/lib/bpf/ringbuf.c
index 02199364db136..8d087bfc7d005 100644
--- a/tools/lib/bpf/ringbuf.c
+++ b/tools/lib/bpf/ringbuf.c
@@ -290,6 +290,21 @@ int ring_buffer__consume(struct ring_buffer *rb)
return res;
}

+/* Consume available data from a single RINGBUF map identified by its ID.
+ * The ring ID is returned in epoll_data by epoll_wait when called with
+ * ring_buffer__epoll_fd.
+ */
+int ring_buffer__consume_ring(struct ring_buffer *rb, uint32_t ring_id)
+{
+ struct ring *ring;
+
+ if (ring_id >= rb->ring_cnt)
+ return libbpf_err(-EINVAL);
+
+ ring = &rb->rings[ring_id];
+ return ringbuf_process_ring(ring);
+}
+
/* Poll for available data and consume records, if any are available.
* Returns number of records consumed (or INT_MAX, whichever is less), or
* negative number, if any of the registered callbacks returned error.
--
2.39.2