samples/bpf: Increment Tx stats at sending

Increment the statistics over how many Tx packets have been sent at
the time of sending instead of at the time of completion. This as a
completion event means that the buffer has been sent AND returned to
user space. The packet always gets sent shortly after sendto() is
called. The kernel might, for performance reasons, decide to not
return every single buffer to user space immediately after sending,
for example, only after a batch of packets have been
transmitted. Incrementing the number of packets sent at completion,
will in that case be confusing as if you send a single packet, the
counter might show zero for a while even though the packet has been
transmitted.

Signed-off-by: Magnus Karlsson <magnus.karlsson@intel.com>
Signed-off-by: Daniel Borkmann <daniel@iogearbox.net>
Acked-by: John Fastabend <john.fastabend@gmail.com>
Link: https://lore.kernel.org/bpf/1605525167-14450-2-git-send-email-magnus.karlsson@gmail.com

diff --git a/samples/bpf/xdpsock_user.c b/samples/bpf/xdpsock_user.c
index 1149e94ca32fd341954304de30beaa5082d6a91d..2567f0db5acab55589fae1d6987522ef49aaebf5 100644 (file)
--- a/samples/bpf/xdpsock_user.c
+++ b/samples/bpf/xdpsock_user.c
@@ -1146,7 +1146,6 @@ static inline void complete_tx_l2fwd(struct xsk_socket_info *xsk,
                xsk_ring_prod__submit(&xsk->umem->fq, rcvd);
                xsk_ring_cons__release(&xsk->umem->cq, rcvd);
                xsk->outstanding_tx -= rcvd;
-               xsk->ring_stats.tx_npkts += rcvd;
        }
 }
 
@@ -1168,7 +1167,6 @@ static inline void complete_tx_only(struct xsk_socket_info *xsk,
        if (rcvd > 0) {
                xsk_ring_cons__release(&xsk->umem->cq, rcvd);
                xsk->outstanding_tx -= rcvd;
-               xsk->ring_stats.tx_npkts += rcvd;
        }
 }
 
@@ -1260,6 +1258,7 @@ static void tx_only(struct xsk_socket_info *xsk, u32 *frame_nb, int batch_size)
        }
 
        xsk_ring_prod__submit(&xsk->tx, batch_size);
+       xsk->ring_stats.tx_npkts += batch_size;
        xsk->outstanding_tx += batch_size;
        *frame_nb += batch_size;
        *frame_nb %= NUM_FRAMES;
@@ -1348,6 +1347,7 @@ static void l2fwd(struct xsk_socket_info *xsk, struct pollfd *fds)
                }
                return;
        }
+       xsk->ring_stats.rx_npkts += rcvd;
 
        ret = xsk_ring_prod__reserve(&xsk->tx, rcvd, &idx_tx);
        while (ret != rcvd) {
@@ -1379,7 +1379,7 @@ static void l2fwd(struct xsk_socket_info *xsk, struct pollfd *fds)
        xsk_ring_prod__submit(&xsk->tx, rcvd);
        xsk_ring_cons__release(&xsk->rx, rcvd);
 
-       xsk->ring_stats.rx_npkts += rcvd;
+       xsk->ring_stats.tx_npkts += rcvd;
        xsk->outstanding_tx += rcvd;
 }