| Message ID | 20240406092005.92399-3-andrea.righi@canonical.com (mailing list archive) |
|---|---|
| State | Accepted |
| Commit | 13e8125a22763557d719db996f70c71f77c9509c |
| Headers | show |
| Series | libbpf: API to partially consume items from ringbuffer | expand |
On Sat, Apr 6, 2024 at 2:20 AM Andrea Righi <andrea.righi@canonical.com> wrote: > > 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: Andrea Righi <andrea.righi@canonical.com> > --- > tools/lib/bpf/ringbuf.c | 23 +++++++++++++++-------- > 1 file changed, 15 insertions(+), 8 deletions(-) > > diff --git a/tools/lib/bpf/ringbuf.c b/tools/lib/bpf/ringbuf.c > index aacb64278a01..2c4031168413 100644 > --- a/tools/lib/bpf/ringbuf.c > +++ b/tools/lib/bpf/ringbuf.c > @@ -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; the idea here was to avoid returning overflown int, not really to stop at INT_MAX samples. So I kept this part intact (res is int64_t, so no overflow inside the loop can happen) > return res; > } > > @@ -314,13 +319,15 @@ 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) { > + res = INT_MAX; > + break; > + } > } > - if (res > INT_MAX) > - return INT_MAX; > return res; > } > > @@ -375,7 +382,7 @@ 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); > > -- > 2.43.0 >
diff --git a/tools/lib/bpf/ringbuf.c b/tools/lib/bpf/ringbuf.c index aacb64278a01..2c4031168413 100644 --- a/tools/lib/bpf/ringbuf.c +++ b/tools/lib/bpf/ringbuf.c @@ -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 +319,15 @@ 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) { + res = INT_MAX; + break; + } } - if (res > INT_MAX) - return INT_MAX; return res; } @@ -375,7 +382,7 @@ 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);
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: Andrea Righi <andrea.righi@canonical.com> --- tools/lib/bpf/ringbuf.c | 23 +++++++++++++++-------- 1 file changed, 15 insertions(+), 8 deletions(-)