libbpf: Add ring__avail_data_size

Add ring__avail_data_size for querying the currently available data in
the ringbuffer, similar to the BPF_RB_AVAIL_DATA flag in
bpf_ringbuf_query. This is racy during ongoing operations but is still
useful for overall information on how a ringbuffer is behaving.

Signed-off-by: Martin Kelly <martin.kelly@crowdstrike.com>
Signed-off-by: Andrii Nakryiko <andrii@kernel.org>
Link: https://lore.kernel.org/bpf/20230925215045.2375758-8-martin.kelly@crowdstrike.com

diff --git a/tools/lib/bpf/libbpf.h b/tools/lib/bpf/libbpf.h
index ab470179b7fea7430e8c13af15ea279fee85fd0d..d60254c5edc6c887633f04afa8ba46ae93cbb0a9 100644 (file)
--- a/tools/lib/bpf/libbpf.h
+++ b/tools/lib/bpf/libbpf.h
@@ -1282,6 +1282,17 @@ LIBBPF_API unsigned long ring__consumer_pos(const struct ring *r);
  */
 LIBBPF_API unsigned long ring__producer_pos(const struct ring *r);
 
+/**
+ * @brief **ring__avail_data_size()** returns the number of bytes in the
+ * ringbuffer not yet consumed. This has no locking associated with it, so it
+ * can be inaccurate if operations are ongoing while this is called. However, it
+ * should still show the correct trend over the long-term.
+ *
+ * @param r A ringbuffer object.
+ * @return The number of bytes not yet consumed.
+ */
+LIBBPF_API size_t ring__avail_data_size(const struct ring *r);
+
 struct user_ring_buffer_opts {
        size_t sz; /* size of this struct, for forward/backward compatibility */
 };

diff --git a/tools/lib/bpf/libbpf.map b/tools/lib/bpf/libbpf.map
index 3bec002449d5fe605aa844efe32e7ce56509a657..5184c94c050269fcb3234a6152fc18fe74c48995 100644 (file)
--- a/tools/lib/bpf/libbpf.map
+++ b/tools/lib/bpf/libbpf.map
@@ -400,6 +400,7 @@ LIBBPF_1.3.0 {
                bpf_program__attach_netfilter;
                bpf_program__attach_tcx;
                bpf_program__attach_uprobe_multi;
+               ring__avail_data_size;
                ring__consumer_pos;
                ring__producer_pos;
                ring_buffer__ring;

diff --git a/tools/lib/bpf/ringbuf.c b/tools/lib/bpf/ringbuf.c
index d14a607f6b664e0584704bc11b93cc45b7eb12d2..07fbc6adcdd9ca2cbf46cb1210c6bf0789683ab8 100644 (file)
--- a/tools/lib/bpf/ringbuf.c
+++ b/tools/lib/bpf/ringbuf.c
@@ -352,6 +352,15 @@ unsigned long ring__producer_pos(const struct ring *r)
        return smp_load_acquire(r->producer_pos);
 }
 
+size_t ring__avail_data_size(const struct ring *r)
+{
+       unsigned long cons_pos, prod_pos;
+
+       cons_pos = ring__consumer_pos(r);
+       prod_pos = ring__producer_pos(r);
+       return prod_pos - cons_pos;
+}
+
 static void user_ringbuf_unmap_ring(struct user_ring_buffer *rb)
 {
        if (rb->consumer_pos) {