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Message-ID: <1d614fdc-3cf1-3558-eb5a-38f16062e57f@gmail.com>
Date: Wed, 25 Mar 2020 22:08:06 +0900
From: Toshiaki Makita <toshiaki.makita1@...il.com>
To: Lorenzo Bianconi <lorenzo@...nel.org>
Cc: netdev@...r.kernel.org, davem@...emloft.net, brouer@...hat.com,
dsahern@...il.com, lorenzo.bianconi@...hat.com, toke@...hat.com
Subject: Re: [PATCH net-next 4/5] veth: introduce more xdp counters
On 2020/03/24 23:36, Lorenzo Bianconi wrote:
>
> [...]
>
>>>> }
>>>
>>> actually I have a different idea..what about account tx stats on the peer rx
>>> queue as a result of XDP_TX or ndo_xdp_xmit and properly report this info in
>>> the ethool stats? In this way we do not have any locking issue and we still use
>>> the per-queue stats approach. Could you please take a look to the following patch?
>>
>> Thanks I think your idea is nice.
>>
>>> diff --git a/drivers/net/veth.c b/drivers/net/veth.c
>>> index b6505a6c7102..f2acd2ee6287 100644
>>> --- a/drivers/net/veth.c
>>> +++ b/drivers/net/veth.c
>>> @@ -92,17 +92,22 @@ struct veth_q_stat_desc {
>>> static const struct veth_q_stat_desc veth_rq_stats_desc[] = {
>>> { "xdp_packets", VETH_RQ_STAT(xdp_packets) },
>>> { "xdp_bytes", VETH_RQ_STAT(xdp_bytes) },
>>> - { "rx_drops", VETH_RQ_STAT(rx_drops) },
>>> - { "rx_xdp_redirect", VETH_RQ_STAT(xdp_redirect) },
>>> - { "rx_xdp_drops", VETH_RQ_STAT(xdp_drops) },
>>> - { "rx_xdp_tx", VETH_RQ_STAT(xdp_tx) },
>>> - { "rx_xdp_tx_errors", VETH_RQ_STAT(xdp_tx_err) },
>>> - { "tx_xdp_xmit", VETH_RQ_STAT(xdp_xmit) },
>>> - { "tx_xdp_xmit_errors", VETH_RQ_STAT(xdp_xmit_err) },
>>> + { "drops", VETH_RQ_STAT(rx_drops) },
>>> + { "xdp_redirect", VETH_RQ_STAT(xdp_redirect) },
>>> + { "xdp_drops", VETH_RQ_STAT(xdp_drops) },
>>> };
>>> #define VETH_RQ_STATS_LEN ARRAY_SIZE(veth_rq_stats_desc)
>>> +static const struct veth_q_stat_desc veth_tq_stats_desc[] = {
>>> + { "xdp_tx", VETH_RQ_STAT(xdp_tx) },
>>> + { "xdp_tx_errors", VETH_RQ_STAT(xdp_tx_err) },
>>
>> I'm wondering why xdp_tx is not accounted in rx_queue?
>> You can count xdp_tx/tx_error somewhere in rx path like veth_xdp_flush_bq().
>> xdp_redirect and xdp_drops are similar actions and in rx stats.
>
> Hi,
>
> thanks for the review :)
>
> I moved the accounting of xdp_tx/tx_error in veth_xdp_xmit for two reason:
> 1- veth_xdp_tx in veth_xdp_rcv_one or veth_xdp_rcv_skb returns an error
> for XDP_TX just if xdp_frame pointer is invalid but the packet can be
> discarded in veth_xdp_xmit if the device is 'under-pressure' (and this can
> be a problem since in XDP there are no queueing mechanisms so far)
Right, but you can track the discard in veth_xdp_flush_bq().
> 2- to be symmetric with ndo_xdp_xmit
I thought consistency between drivers is more important. What about other drivers?
Toshiaki Makita
>
>>
>>> + { "xdp_xmit", VETH_RQ_STAT(xdp_xmit) },
>>> + { "xdp_xmit_errors", VETH_RQ_STAT(xdp_xmit_err) },
>>> +};
>>> +
>>> +#define VETH_TQ_STATS_LEN ARRAY_SIZE(veth_tq_stats_desc)
>>> +
>>> static struct {
>>> const char string[ETH_GSTRING_LEN];
>>> } ethtool_stats_keys[] = {
>>> @@ -142,6 +147,14 @@ static void veth_get_strings(struct net_device *dev, u32 stringset, u8 *buf)
>>> p += ETH_GSTRING_LEN;
>>> }
>>> }
>>> + for (i = 0; i < dev->real_num_tx_queues; i++) {
>>> + for (j = 0; j < VETH_TQ_STATS_LEN; j++) {
>>> + snprintf(p, ETH_GSTRING_LEN,
>>> + "tx_queue_%u_%.18s",
>>> + i, veth_tq_stats_desc[j].desc);
>>> + p += ETH_GSTRING_LEN;
>>> + }
>>> + }
>>> break;
>>> }
>>> }
>>> @@ -151,7 +164,8 @@ static int veth_get_sset_count(struct net_device *dev, int sset)
>>> switch (sset) {
>>> case ETH_SS_STATS:
>>> return ARRAY_SIZE(ethtool_stats_keys) +
>>> - VETH_RQ_STATS_LEN * dev->real_num_rx_queues;
>>> + VETH_RQ_STATS_LEN * dev->real_num_rx_queues +
>>> + VETH_TQ_STATS_LEN * dev->real_num_tx_queues;
>>> default:
>>> return -EOPNOTSUPP;
>>> }
>>> @@ -160,7 +174,7 @@ static int veth_get_sset_count(struct net_device *dev, int sset)
>>> static void veth_get_ethtool_stats(struct net_device *dev,
>>> struct ethtool_stats *stats, u64 *data)
>>> {
>>> - struct veth_priv *priv = netdev_priv(dev);
>>> + struct veth_priv *rcv_priv, *priv = netdev_priv(dev);
>>> struct net_device *peer = rtnl_dereference(priv->peer);
>>> int i, j, idx;
>>> @@ -181,6 +195,26 @@ static void veth_get_ethtool_stats(struct net_device *dev,
>>> } while (u64_stats_fetch_retry_irq(&rq_stats->syncp, start));
>>> idx += VETH_RQ_STATS_LEN;
>>> }
>>> +
>>> + if (!peer)
>>> + return;
>>> +
>>> + rcv_priv = netdev_priv(peer);
>>> + for (i = 0; i < peer->real_num_rx_queues; i++) {
>>> + const struct veth_rq_stats *rq_stats = &rcv_priv->rq[i].stats;
>>> + const void *stats_base = (void *)&rq_stats->vs;
>>> + unsigned int start, tx_idx;
>>> + size_t offset;
>>> +
>>> + tx_idx = (i % dev->real_num_tx_queues) * VETH_TQ_STATS_LEN;
>>
>> I'm a bit concerned that this can fold multiple rx queue counters into one
>> tx counter. But I cannot think of a better idea provided that we want to
>> align XDP stats between drivers. So I'm OK with this.
>
> Since peer->real_num_rx_queues can be greater than dev->real_num_tx_queues,
> right? IIUC the only guarantee we have is:
>
> peer->real_num_tx_queues < dev->real_num_rx_queues
>
> If you are fine with that approach, I will post a patch before net-next
> closure.
>
> Regards,
> Lorenzo
>
>
>>
>> Toshiaki Makita
>>
>>> + do {
>>> + start = u64_stats_fetch_begin_irq(&rq_stats->syncp);
>>> + for (j = 0; j < VETH_TQ_STATS_LEN; j++) {
>>> + offset = veth_tq_stats_desc[j].offset;
>>> + data[tx_idx + idx + j] += *(u64 *)(stats_base + offset);
>>> + }
>>> + } while (u64_stats_fetch_retry_irq(&rq_stats->syncp, start));
>>> + }
>>> }
>>> static const struct ethtool_ops veth_ethtool_ops = {
>>> @@ -340,8 +374,7 @@ static void veth_get_stats64(struct net_device *dev,
>>> tot->tx_packets = packets;
>>> veth_stats_rx(&rx, dev);
>>> - tot->tx_dropped += rx.xdp_xmit_err + rx.xdp_tx_err;
>>> - tot->rx_dropped = rx.rx_drops;
>>> + tot->rx_dropped = rx.rx_drops + rx.xdp_tx_err + rx.xdp_xmit_err;
>>> tot->rx_bytes = rx.xdp_bytes;
>>> tot->rx_packets = rx.xdp_packets;
>>> @@ -353,7 +386,7 @@ static void veth_get_stats64(struct net_device *dev,
>>> tot->rx_packets += packets;
>>> veth_stats_rx(&rx, peer);
>>> - tot->rx_dropped += rx.xdp_xmit_err + rx.xdp_tx_err;
>>> + tot->tx_dropped += rx.xdp_xmit_err + rx.xdp_tx_err;
>>> tot->tx_bytes += rx.xdp_bytes;
>>> tot->tx_packets += rx.xdp_packets;
>>> }
>>> @@ -394,9 +427,9 @@ static int veth_xdp_xmit(struct net_device *dev, int n,
>>> u32 flags, bool ndo_xmit)
>>> {
>>> struct veth_priv *rcv_priv, *priv = netdev_priv(dev);
>>> - unsigned int qidx, max_len;
>>> struct net_device *rcv;
>>> int i, ret, drops = n;
>>> + unsigned int max_len;
>>> struct veth_rq *rq;
>>> rcu_read_lock();
>>> @@ -414,8 +447,7 @@ static int veth_xdp_xmit(struct net_device *dev, int n,
>>> }
>>> rcv_priv = netdev_priv(rcv);
>>> - qidx = veth_select_rxq(rcv);
>>> - rq = &rcv_priv->rq[qidx];
>>> + rq = &rcv_priv->rq[veth_select_rxq(rcv)];
>>> /* Non-NULL xdp_prog ensures that xdp_ring is initialized on receive
>>> * side. This means an XDP program is loaded on the peer and the peer
>>> * device is up.
>>> @@ -446,7 +478,6 @@ static int veth_xdp_xmit(struct net_device *dev, int n,
>>> ret = n - drops;
>>> drop:
>>> - rq = &priv->rq[qidx];
>>> u64_stats_update_begin(&rq->stats.syncp);
>>> if (ndo_xmit) {
>>> rq->stats.vs.xdp_xmit += n - drops;
>>>
>>>>
>>>> Thoughts?
>>>>
>>>> Toshiaki Makita
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