mvneta: add XDP ethtool errors stats for TX to driver

Adding ethtool stats for when XDP transmitted packets overrun the TX
queue. This is recorded separately for XDP_TX and ndo_xdp_xmit. This
is an important aid for troubleshooting XDP based setups.

It is currently a known weakness and property of XDP that there isn't
any push-back or congestion feedback when transmitting frames via XDP.
It's easy to realise when redirecting from a higher speed link into a
slower speed link, or simply two ingress links into a single egress.
The situation can also happen when Ethernet flow control is active.

For testing the patch and provoking the situation to occur on my
Espressobin board, I configured the TX-queue to be smaller (434) than
RX-queue (512) and overload network with large MTU size frames (as a
larger frame takes longer to transmit).

Hopefully the upcoming XDP TX hook can be extended to provide insight
into these TX queue overflows, to allow programmable adaptation
strategies.

Signed-off-by: Jesper Dangaard Brouer <brouer@redhat.com>
Acked-by: Lorenzo Bianconi <lorenzo@kernel.org>
Signed-off-by: David S. Miller <davem@davemloft.net>

diff --git a/drivers/net/ethernet/marvell/mvneta.c b/drivers/net/ethernet/marvell/mvneta.c
index b22eeb5..bc488e8 100644 (file)
--- a/drivers/net/ethernet/marvell/mvneta.c
+++ b/drivers/net/ethernet/marvell/mvneta.c
@@ -344,8 +344,10 @@ enum {
        ETHTOOL_XDP_REDIRECT,
        ETHTOOL_XDP_PASS,
        ETHTOOL_XDP_DROP,
-       ETHTOOL_XDP_XMIT,
        ETHTOOL_XDP_TX,
+       ETHTOOL_XDP_TX_ERR,
+       ETHTOOL_XDP_XMIT,
+       ETHTOOL_XDP_XMIT_ERR,
        ETHTOOL_MAX_STATS,
 };
 
@@ -404,7 +406,9 @@ static const struct mvneta_statistic mvneta_statistics[] = {
        { ETHTOOL_XDP_PASS, T_SW, "rx_xdp_pass", },
        { ETHTOOL_XDP_DROP, T_SW, "rx_xdp_drop", },
        { ETHTOOL_XDP_TX, T_SW, "rx_xdp_tx", },
+       { ETHTOOL_XDP_TX_ERR, T_SW, "rx_xdp_tx_errors", },
        { ETHTOOL_XDP_XMIT, T_SW, "tx_xdp_xmit", },
+       { ETHTOOL_XDP_XMIT_ERR, T_SW, "tx_xdp_xmit_errors", },
 };
 
 struct mvneta_stats {
@@ -417,7 +421,9 @@ struct mvneta_stats {
        u64     xdp_pass;
        u64     xdp_drop;
        u64     xdp_xmit;
+       u64     xdp_xmit_err;
        u64     xdp_tx;
+       u64     xdp_tx_err;
 };
 
 struct mvneta_ethtool_stats {
@@ -2059,6 +2065,7 @@ mvneta_xdp_submit_frame(struct mvneta_port *pp, struct mvneta_tx_queue *txq,
 static int
 mvneta_xdp_xmit_back(struct mvneta_port *pp, struct xdp_buff *xdp)
 {
+       struct mvneta_pcpu_stats *stats = this_cpu_ptr(pp->stats);
        struct mvneta_tx_queue *txq;
        struct netdev_queue *nq;
        struct xdp_frame *xdpf;
@@ -2076,8 +2083,6 @@ mvneta_xdp_xmit_back(struct mvneta_port *pp, struct xdp_buff *xdp)
        __netif_tx_lock(nq, cpu);
        ret = mvneta_xdp_submit_frame(pp, txq, xdpf, false);
        if (ret == MVNETA_XDP_TX) {
-               struct mvneta_pcpu_stats *stats = this_cpu_ptr(pp->stats);
-
                u64_stats_update_begin(&stats->syncp);
                stats->es.ps.tx_bytes += xdpf->len;
                stats->es.ps.tx_packets++;
@@ -2085,6 +2090,10 @@ mvneta_xdp_xmit_back(struct mvneta_port *pp, struct xdp_buff *xdp)
                u64_stats_update_end(&stats->syncp);
 
                mvneta_txq_pend_desc_add(pp, txq, 0);
+       } else {
+               u64_stats_update_begin(&stats->syncp);
+               stats->es.ps.xdp_tx_err++;
+               u64_stats_update_end(&stats->syncp);
        }
        __netif_tx_unlock(nq);
 
@@ -2128,6 +2137,7 @@ mvneta_xdp_xmit(struct net_device *dev, int num_frame,
        stats->es.ps.tx_bytes += nxmit_byte;
        stats->es.ps.tx_packets += nxmit;
        stats->es.ps.xdp_xmit += nxmit;
+       stats->es.ps.xdp_xmit_err += num_frame - nxmit;
        u64_stats_update_end(&stats->syncp);
 
        return nxmit;
@@ -2152,7 +2162,7 @@ mvneta_run_xdp(struct mvneta_port *pp, struct mvneta_rx_queue *rxq,
                int err;
 
                err = xdp_do_redirect(pp->dev, xdp, prog);
-               if (err) {
+               if (unlikely(err)) {
                        ret = MVNETA_XDP_DROPPED;
                        page_pool_put_page(rxq->page_pool,
                                           virt_to_head_page(xdp->data), len,
@@ -4518,6 +4528,8 @@ mvneta_ethtool_update_pcpu_stats(struct mvneta_port *pp,
                u64 skb_alloc_error;
                u64 refill_error;
                u64 xdp_redirect;
+               u64 xdp_xmit_err;
+               u64 xdp_tx_err;
                u64 xdp_pass;
                u64 xdp_drop;
                u64 xdp_xmit;
@@ -4532,7 +4544,9 @@ mvneta_ethtool_update_pcpu_stats(struct mvneta_port *pp,
                        xdp_pass = stats->es.ps.xdp_pass;
                        xdp_drop = stats->es.ps.xdp_drop;
                        xdp_xmit = stats->es.ps.xdp_xmit;
+                       xdp_xmit_err = stats->es.ps.xdp_xmit_err;
                        xdp_tx = stats->es.ps.xdp_tx;
+                       xdp_tx_err = stats->es.ps.xdp_tx_err;
                } while (u64_stats_fetch_retry_irq(&stats->syncp, start));
 
                es->skb_alloc_error += skb_alloc_error;
@@ -4541,7 +4555,9 @@ mvneta_ethtool_update_pcpu_stats(struct mvneta_port *pp,
                es->ps.xdp_pass += xdp_pass;
                es->ps.xdp_drop += xdp_drop;
                es->ps.xdp_xmit += xdp_xmit;
+               es->ps.xdp_xmit_err += xdp_xmit_err;
                es->ps.xdp_tx += xdp_tx;
+               es->ps.xdp_tx_err += xdp_tx_err;
        }
 }
 
@@ -4594,9 +4610,15 @@ static void mvneta_ethtool_update_stats(struct mvneta_port *pp)
                        case ETHTOOL_XDP_TX:
                                pp->ethtool_stats[i] = stats.ps.xdp_tx;
                                break;
+                       case ETHTOOL_XDP_TX_ERR:
+                               pp->ethtool_stats[i] = stats.ps.xdp_tx_err;
+                               break;
                        case ETHTOOL_XDP_XMIT:
                                pp->ethtool_stats[i] = stats.ps.xdp_xmit;
                                break;
+                       case ETHTOOL_XDP_XMIT_ERR:
+                               pp->ethtool_stats[i] = stats.ps.xdp_xmit_err;
+                               break;
                        }
                        break;
                }