Re: [PATCH net-next v2 1/1] net/mlx5e: Add per queue netdev-genl stats

From: Tariq Toukan
Date: Thu May 23 2024 - 03:28:15 EST

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On 15/05/2024 10:19, Joe Damato wrote:

On Tue, May 14, 2024 at 09:44:37PM +0300, Tariq Toukan wrote:

On 10/05/2024 7:17, Joe Damato wrote:

Add functions to support the netdev-genl per queue stats API.

./cli.py --spec netlink/specs/netdev.yaml \
--dump qstats-get --json '{"scope": "queue"}'

...snip

{'ifindex': 7,
'queue-id': 62,
'queue-type': 'rx',
'rx-alloc-fail': 0,
'rx-bytes': 105965251,
'rx-packets': 179790},
{'ifindex': 7,
'queue-id': 0,
'queue-type': 'tx',
'tx-bytes': 9402665,
'tx-packets': 17551},

...snip

Also tested with the script tools/testing/selftests/drivers/net/stats.py
in several scenarios to ensure stats tallying was correct:

- on boot (default queue counts)
- adjusting queue count up or down (ethtool -L eth0 combined ...)
- adding mqprio TCs

Signed-off-by: Joe Damato <jdamato@xxxxxxxxxx>
---
.../net/ethernet/mellanox/mlx5/core/en_main.c | 144 ++++++++++++++++++
1 file changed, 144 insertions(+)

diff --git a/drivers/net/ethernet/mellanox/mlx5/core/en_main.c b/drivers/net/ethernet/mellanox/mlx5/core/en_main.c
index ffe8919494d5..4a675d8b31b5 100644
--- a/drivers/net/ethernet/mellanox/mlx5/core/en_main.c
+++ b/drivers/net/ethernet/mellanox/mlx5/core/en_main.c
@@ -39,6 +39,7 @@
#include <linux/debugfs.h>
#include <linux/if_bridge.h>
#include <linux/filter.h>
+#include <net/netdev_queues.h>
#include <net/page_pool/types.h>
#include <net/pkt_sched.h>
#include <net/xdp_sock_drv.h>
@@ -5282,6 +5283,148 @@ static bool mlx5e_tunnel_any_tx_proto_supported(struct mlx5_core_dev *mdev)
return (mlx5_vxlan_allowed(mdev->vxlan) || mlx5_geneve_tx_allowed(mdev));
}
+static void mlx5e_get_queue_stats_rx(struct net_device *dev, int i,
+ struct netdev_queue_stats_rx *stats)
+{
+ struct mlx5e_priv *priv = netdev_priv(dev);
+
+ if (mlx5e_is_uplink_rep(priv))
+ return;
+
+ struct mlx5e_channel_stats *channel_stats = priv->channel_stats[i];
+ struct mlx5e_rq_stats *xskrq_stats = &channel_stats->xskrq;
+ struct mlx5e_rq_stats *rq_stats = &channel_stats->rq;
+

Don't we allow variable declaration only at the beginning of a block?
Is this style accepted in the networking subsystem?

+ stats->packets = rq_stats->packets + xskrq_stats->packets;
+ stats->bytes = rq_stats->bytes + xskrq_stats->bytes;
+ stats->alloc_fail = rq_stats->buff_alloc_err +
+ xskrq_stats->buff_alloc_err;
+}
+
+static void mlx5e_get_queue_stats_tx(struct net_device *dev, int i,
+ struct netdev_queue_stats_tx *stats)
+{
+ struct mlx5e_priv *priv = netdev_priv(dev);
+ struct net_device *netdev = priv->netdev;
+ struct mlx5e_txqsq *sq;
+ int j;
+
+ if (mlx5e_is_uplink_rep(priv))
+ return;
+
+ for (j = 0; j < netdev->num_tx_queues; j++) {
+ sq = priv->txq2sq[j];

No sq instance in case interface is down.

This seems easily fixable by checking:

priv->channels.num > 0

yes, or test_bit(MLX5E_STATE_OPENED, &priv->state).

This should be a simple arithmetic calculation.

I'm not sure why I can't use txq2sq? Please see below for my
explanation about why I think txq2sq might be all I need.

Need to expose the proper functions for this calculation, and use it here
and in the sq create flows.

I re-read the code several times and my apologies, but I am probably
still missing something.

I don't think a calculation function is necessary (see below), but
if one is really needed, I'd probably add something like:

static inline int tc_to_txq_ix(struct mlx5e_channel *c,
struct mlx5e_params *params,
int tc)
{
return c->ix + tc * params->num_channels;

We need the opposite direction.

The goal is to calculate the proper pair of (ch_ix, tc) in order to access the correct sq_stats struct in the stats array:
priv->channel_stats[ch_ix]->sq[tc];

Given i in [0, real_num_tx_queues), we should extract the pair as follows:

ch_ix = i % params->num_channels;
tc = i / params->num_channels;

}

And call it from mlx5e_open_sqs.

But, I don't understand why any calculation is needed in
mlx5e_get_queue_stats_tx. Please see below for explanation.

Here it seems that you need a very involved user, so he passes the correct
index i of the SQ that he's interested in..

+ if (sq->ch_ix == i) {

So you're looking for the first SQ on channel i?
But there might be multiple SQs on channel i...
Also, this SQ might be already included in the base stats.
In addition, this i might be too large for a channel index (num_tx_queues
can be 8 * num_channels)

The logic here (of mapping from i in num_tx_queues to SQ stats) needs
careful definition.

I read your comments a few times and read the mlx5 source and I am
probably still missing something obvious here; my apologies.

In net/core/netdev-genl.c, calls to the driver's get_queue_stats_tx
appear to pass [0, netdev->real_num_tx_queues) as i.

I think this means i is a txq_ix in mlx5, because mlx5 sets
netdev->real_num_tx_queues in mlx5e_update_tx_netdev_queues, as:

nch * ntc + qos_queues

which when expanded is

priv->channels.params.num_channels * mlx5e_get_dcb_num_tc + qos_queues

So, net/core/netdev-genl.c will be using 0 up to that expression as
i when calling mlx5e_get_queue_stats_tx.

Right.

In mlx5:
- mlx5e_activate_priv_channels calls mlx5e_build_txq_maps which
generates priv->txq2sq[txq_ix] = sq for every mlx5e_get_dcb_num_tc
of every priv->channels.num.
This seems to happen every time mlx5e_activate_priv_channels is
called, which I think means that priv->txq2sq is always up to date
and will give the right sq for a given txq_ix (assuming the device
isn't down).

Right.

Putting all of this together, I think that mlx5e_get_queue_stats_tx
might need to be something like:

mutex_lock(&priv->state_lock);
if (priv->channels.num > 0) {
sq = priv->txq2sq[i];
stats->packets = sq->stats->packets;
stats->bytes = sq->stats->bytes;
}
mutex_unlock(&priv->state_lock);

Right.
But you can also access the sq_stats directly without going through the sq. This is important as the channels might be down.

Is this still incorrect somehow?

If so, could you explain a bit more about why a calculation is
needed? It seems like txq2sq would provide the mapping from txq_ix's
(which is what mlx5e_get_queue_stats_tx gets as 'i') and an sq,
which seems like all I would need?

Sorry if I am still not following here.

I see two possible solutions:

1.
a. in the base, sum all stats for entries that are no longer available in the current configuration (independently to if the netdev is up or down), like sqs for ch_ix >= params->num_channels.
b. in mlx5e_get_queue_stats_tx, access the sq_stats without going through the sq (as it might not exist), this will be done for all i in 0 ti real_num_tx_queues.

2.
a. in the base, sum all stats for all non existing sqs. if interface is down, then no sqs exist, so you sum the whole array.
b. in mlx5e_get_queue_stats_tx, go through the txq2sq and the sq, if it exists, if interface is down just return empty stats.

I don't have strong preference, although #1 looks slightly better to me.

+ stats->packets = sq->stats->packets;
+ stats->bytes = sq->stats->bytes;
+ return;
+ }
+ }
+}
+
+static void mlx5e_get_base_stats(struct net_device *dev,
+ struct netdev_queue_stats_rx *rx,
+ struct netdev_queue_stats_tx *tx)
+{
+ struct mlx5e_priv *priv = netdev_priv(dev);
+ int i, j;
+
+ if (!mlx5e_is_uplink_rep(priv)) {
+ rx->packets = 0;
+ rx->bytes = 0;
+ rx->alloc_fail = 0;
+
+ /* compute stats for deactivated RX queues
+ *
+ * if priv->channels.num == 0 the device is down, so compute
+ * stats for every queue.
+ *
+ * otherwise, compute only the queues which have been deactivated.
+ */
+ if (priv->channels.num == 0)
+ i = 0;
+ else
+ i = priv->channels.params.num_channels;
+
+ for (; i < priv->stats_nch; i++) {
+ struct mlx5e_channel_stats *channel_stats = priv->channel_stats[i];
+ struct mlx5e_rq_stats *xskrq_stats = &channel_stats->xskrq;
+ struct mlx5e_rq_stats *rq_stats = &channel_stats->rq;
+
+ rx->packets += rq_stats->packets + xskrq_stats->packets;
+ rx->bytes += rq_stats->bytes + xskrq_stats->bytes;
+ rx->alloc_fail += rq_stats->buff_alloc_err +
+ xskrq_stats->buff_alloc_err;

Isn't this equivalent to mlx5e_get_queue_stats_rx(i) ?

+ }
+
+ if (priv->rx_ptp_opened) {
+ struct mlx5e_rq_stats *rq_stats = &priv->ptp_stats.rq;
+
+ rx->packets += rq_stats->packets;
+ rx->bytes += rq_stats->bytes;
+ }
+ }
+
+ tx->packets = 0;
+ tx->bytes = 0;
+
+ /* three TX cases to handle:
+ *
+ * case 1: priv->channels.num == 0, get the stats for every TC
+ * on every queue.
+ *
+ * case 2: priv->channel.num > 0, so get the stats for every TC on
+ * every deactivated queue.
+ *
+ * case 3: the number of TCs has changed, so get the stats for the
+ * inactive TCs on active TX queues (handled in the second loop
+ * below).
+ */
+ if (priv->channels.num == 0)
+ i = 0;
+ else
+ i = priv->channels.params.num_channels;
+

All reads/writes to priv->channels must be under the priv->state_lock.

+ for (; i < priv->stats_nch; i++) {
+ struct mlx5e_channel_stats *channel_stats = priv->channel_stats[i];
+
+ for (j = 0; j < priv->max_opened_tc; j++) {
+ struct mlx5e_sq_stats *sq_stats = &channel_stats->sq[j];
+
+ tx->packets += sq_stats->packets;
+ tx->bytes += sq_stats->bytes;
+ }
+ }
+
+ /* Handle case 3 described above. */
+ for (i = 0; i < priv->channels.params.num_channels; i++) {
+ struct mlx5e_channel_stats *channel_stats = priv->channel_stats[i];
+ u8 dcb_num_tc = mlx5e_get_dcb_num_tc(&priv->channels.params);
+
+ for (j = dcb_num_tc; j < priv->max_opened_tc; j++) {
+ struct mlx5e_sq_stats *sq_stats = &channel_stats->sq[j];
+
+ tx->packets += sq_stats->packets;
+ tx->bytes += sq_stats->bytes;
+ }
+ }
+
+ if (priv->tx_ptp_opened) {
+ for (j = 0; j < priv->max_opened_tc; j++) {
+ struct mlx5e_sq_stats *sq_stats = &priv->ptp_stats.sq[j];
+
+ tx->packets += sq_stats->packets;
+ tx->bytes += sq_stats->bytes;
+ }
+ }
+}
+
+static const struct netdev_stat_ops mlx5e_stat_ops = {
+ .get_queue_stats_rx = mlx5e_get_queue_stats_rx,
+ .get_queue_stats_tx = mlx5e_get_queue_stats_tx,
+ .get_base_stats = mlx5e_get_base_stats,
+};
+
static void mlx5e_build_nic_netdev(struct net_device *netdev)
{
struct mlx5e_priv *priv = netdev_priv(netdev);
@@ -5299,6 +5442,7 @@ static void mlx5e_build_nic_netdev(struct net_device *netdev)
netdev->watchdog_timeo = 15 * HZ;
+ netdev->stat_ops = &mlx5e_stat_ops;
netdev->ethtool_ops = &mlx5e_ethtool_ops;
netdev->vlan_features |= NETIF_F_SG;

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