Commit 13e8125a authored by Andrea Righi's avatar Andrea Righi Committed by Andrii Nakryiko
Browse files

libbpf: ringbuf: Allow to consume up to a certain amount of items 



In some cases, instead of always consuming all items from ring buffers
in a greedy way, we may want to consume up to a certain amount of items,
for example when we need to copy items from the BPF ring buffer to a
limited user buffer.

This change allows to set an upper limit to the amount of items consumed
from one or more ring buffers.

Signed-off-by: default avatarAndrea Righi <andrea.righi@canonical.com>
Signed-off-by: default avatarAndrii Nakryiko <andrii@kernel.org>
Link: https://lore.kernel.org/bpf/20240406092005.92399-3-andrea.righi@canonical.com
parent 5bd2ed65

tools/lib/bpf/ringbuf.c

+12 −7
Original line number Diff line number Diff line
@@ -231,7 +231,7 @@ static inline int roundup_len(__u32 len) 
	return (len + 7) / 8 * 8;

}



static int64_t ringbuf_process_ring(struct ring *r)

static int64_t ringbuf_process_ring(struct ring *r, size_t n)

{

	int *len_ptr, len, err;

	/* 64-bit to avoid overflow in case of extreme application behavior */
@@ -268,6 +268,9 @@ static int64_t ringbuf_process_ring(struct ring *r) 
			}



			smp_store_release(r->consumer_pos, cons_pos);



			if (cnt >= n)

				goto done;

		}

	} while (got_new_data);

done:
@@ -287,13 +290,15 @@ int ring_buffer__consume(struct ring_buffer *rb) 
	for (i = 0; i < rb->ring_cnt; i++) {

		struct ring *ring = rb->rings[i];



		err = ringbuf_process_ring(ring);

		err = ringbuf_process_ring(ring, INT_MAX);

		if (err < 0)

			return libbpf_err(err);

		res += err;

		if (res > INT_MAX) {

			res = INT_MAX;

			break;

		}

	}

	if (res > INT_MAX)

		return INT_MAX;

	return res;

}
@@ -314,13 +319,13 @@ int ring_buffer__poll(struct ring_buffer *rb, int timeout_ms) 
		__u32 ring_id = rb->events[i].data.fd;

		struct ring *ring = rb->rings[ring_id];



		err = ringbuf_process_ring(ring);

		err = ringbuf_process_ring(ring, INT_MAX);

		if (err < 0)

			return libbpf_err(err);

		res += err;

	}

	if (res > INT_MAX)

		return INT_MAX;

		res = INT_MAX;

	return res;

}
@@ -375,7 +380,7 @@ int ring__consume(struct ring *r) 
{

	int64_t res;



	res = ringbuf_process_ring(r);

	res = ringbuf_process_ring(r, INT_MAX);

	if (res < 0)

		return libbpf_err(res);