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Date: Mon, 2 Mar 2020 15:13:05 +0100
From: Lorenzo Bianconi <lorenzo@...nel.org>
To: Jesper Dangaard Brouer <brouer@...hat.com>
Cc: netdev@...r.kernel.org, "David S. Miller" <davem@...emloft.net>,
Ilias Apalodimas <ilias.apalodimas@...aro.org>,
David Ahern <dsahern@...il.com>,
Toke Høiland-Jørgensen <toke@...e.dk>,
Saeed Mahameed <saeedm@...lanox.com>,
Tariq Toukan <tariqt@...lanox.com>, kuba@...nel.org,
andrew@...n.ch, thomas.petazzoni@...tlin.com
Subject: Re: [net-next PATCH] 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@...hat.com>
This was on my ToDo list, thx for working on this :)
Acked-by: Lorenzo Bianconi <lorenzo@...nel.org>
> ---
> drivers/net/ethernet/marvell/mvneta.c | 30 ++++++++++++++++++++++++++----
> 1 file changed, 26 insertions(+), 4 deletions(-)
>
> diff --git a/drivers/net/ethernet/marvell/mvneta.c b/drivers/net/ethernet/marvell/mvneta.c
> index b22eeb5f8700..bc488e8b8e45 100644
> --- 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;
> }
>
>
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