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libbpf: Add ring__consume_n / ring_buffer__consume_n

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Introduce a new API to consume items from a ring buffer, limited to a
specified amount, and return to the caller the actual number of items
consumed.

Signed-off-by: Andrea Righi <andrea.righi@canonical.com>
Signed-off-by: Andrii Nakryiko <andrii@kernel.org>
Link: https://lore.kernel.org/lkml/20240310154726.734289-1-andrea.righi@canonical.com/T
Link: https://lore.kernel.org/bpf/20240406092005.92399-4-andrea.righi@canonical.com
This commit is contained in:
Andrea Righi 2024-04-06 11:15:43 +02:00 committed by Andrii Nakryiko
parent 13e8125a22
commit 4d22ea94ea
3 changed files with 50 additions and 3 deletions
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12
tools/lib/bpf/libbpf.h
View file

@ -1293,6 +1293,7 @@ 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_n(struct ring_buffer *rb, size_t n);
LIBBPF_API int ring_buffer__epoll_fd(const struct ring_buffer *rb);
/**
@ -1367,6 +1368,17 @@ LIBBPF_API int ring__map_fd(const struct ring *r);
*/
LIBBPF_API int ring__consume(struct ring *r);
/**
* @brief **ring__consume_n()** consumes up to a requested amount of items from
* a ringbuffer without event polling.
*
* @param r A ringbuffer object.
* @param n Maximum amount of items to consume.
* @return The number of items consumed, or a negative number if any of the
* callbacks return an error.
*/
LIBBPF_API int ring__consume_n(struct ring *r, size_t n);
struct user_ring_buffer_opts {
size_t sz; /* size of this struct, for forward/backward compatibility */
};

3
tools/lib/bpf/libbpf.map
View file

@ -418,4 +418,7 @@ LIBBPF_1.4.0 {
} LIBBPF_1.3.0;
LIBBPF_1.5.0 {
global:
ring__consume_n;
ring_buffer__consume_n;
} LIBBPF_1.4.0;

38
tools/lib/bpf/ringbuf.c
View file

@ -277,6 +277,33 @@ static int64_t ringbuf_process_ring(struct ring *r, size_t n)
return cnt;
}
/* Consume available ring buffer(s) data without event polling, up to n
* records.
*
* Returns number of records consumed across all registered ring buffers (or
* n, whichever is less), or negative number if any of the callbacks return
* error.
*/
int ring_buffer__consume_n(struct ring_buffer *rb, size_t n)
{
int64_t err, res = 0;
int i;
for (i = 0; i < rb->ring_cnt; i++) {
struct ring *ring = rb->rings[i];
err = ringbuf_process_ring(ring, n);
if (err < 0)
return libbpf_err(err);
res += err;
n -= err;
if (n == 0)
break;
}
return res;
}
/* Consume available ring buffer(s) data without event polling.
* Returns number of records consumed across all registered ring buffers (or
* INT_MAX, whichever is less), or negative number if any of the callbacks
@ -376,17 +403,22 @@ int ring__map_fd(const struct ring *r)
return r->map_fd;
}
int ring__consume(struct ring *r)
int ring__consume_n(struct ring *r, size_t n)
{
int64_t res;
int res;
res = ringbuf_process_ring(r, INT_MAX);
res = ringbuf_process_ring(r, n);
if (res < 0)
return libbpf_err(res);
return res > INT_MAX ? INT_MAX : res;
}
int ring__consume(struct ring *r)
{
return ring__consume_n(r, INT_MAX);
}
static void user_ringbuf_unmap_ring(struct user_ring_buffer *rb)
{
if (rb->consumer_pos) {