Re: [PATCH v2] hv_netvsc: Add per-cpu ethtool stats for netvsc

From: Stephen Hemminger
Date: Wed Jun 13 2018 - 17:48:22 EST


On Wed, 13 Jun 2018 12:36:08 -0700
Yidong Ren <yidren@xxxxxxxxxxxxxxxxx> wrote:

> From: Yidong Ren <yidren@xxxxxxxxxxxxx>
>
> This patch implements following ethtool stats fields for netvsc:
> cpu<n>_tx/rx_packets/bytes
> cpu<n>_vf_tx/rx_packets/bytes
>
> Corresponding per-cpu counters exist in current code. Exposing these
> counters will help troubleshooting performance issues.
>
> Signed-off-by: Yidong Ren <yidren@xxxxxxxxxxxxx>
> ---
> Changes in v2:
> - Remove cpp style comment
> - Resubmit after freeze
>
> drivers/net/hyperv/hyperv_net.h | 11 +++++
> drivers/net/hyperv/netvsc_drv.c | 104 +++++++++++++++++++++++++++++++++++++++-
> 2 files changed, 113 insertions(+), 2 deletions(-)
>
> diff --git a/drivers/net/hyperv/hyperv_net.h b/drivers/net/hyperv/hyperv_net.h
> index 23304ac..c825353 100644
> --- a/drivers/net/hyperv/hyperv_net.h
> +++ b/drivers/net/hyperv/hyperv_net.h
> @@ -873,6 +873,17 @@ struct netvsc_ethtool_stats {
> unsigned long wake_queue;
> };
>
> +struct netvsc_ethtool_pcpu_stats {
> + u64 rx_packets;
> + u64 rx_bytes;
> + u64 tx_packets;
> + u64 tx_bytes;
> + u64 vf_rx_packets;
> + u64 vf_rx_bytes;
> + u64 vf_tx_packets;
> + u64 vf_tx_bytes;
> +};
> +
> struct netvsc_vf_pcpu_stats {
> u64 rx_packets;
> u64 rx_bytes;
> diff --git a/drivers/net/hyperv/netvsc_drv.c b/drivers/net/hyperv/netvsc_drv.c
> index 7b18a8c..6803aae 100644
> --- a/drivers/net/hyperv/netvsc_drv.c
> +++ b/drivers/net/hyperv/netvsc_drv.c
> @@ -1105,6 +1105,66 @@ static void netvsc_get_vf_stats(struct net_device *net,
> }
> }
>
> +static void netvsc_get_pcpu_stats(struct net_device *net,
> + struct netvsc_ethtool_pcpu_stats
> + __percpu *pcpu_tot)
> +{
> + struct net_device_context *ndev_ctx = netdev_priv(net);
> + struct netvsc_device *nvdev = rcu_dereference_rtnl(ndev_ctx->nvdev);
> + int i;
> +
> + /* fetch percpu stats of vf */
> + for_each_possible_cpu(i) {
> + const struct netvsc_vf_pcpu_stats *stats =
> + per_cpu_ptr(ndev_ctx->vf_stats, i);
> + struct netvsc_ethtool_pcpu_stats *this_tot =
> + per_cpu_ptr(pcpu_tot, i);
> + unsigned int start;
> +
> + do {
> + start = u64_stats_fetch_begin_irq(&stats->syncp);
> + this_tot->vf_rx_packets = stats->rx_packets;
> + this_tot->vf_tx_packets = stats->tx_packets;
> + this_tot->vf_rx_bytes = stats->rx_bytes;
> + this_tot->vf_tx_bytes = stats->tx_bytes;
> + } while (u64_stats_fetch_retry_irq(&stats->syncp, start));
> + this_tot->rx_packets = this_tot->vf_rx_packets;
> + this_tot->tx_packets = this_tot->vf_tx_packets;
> + this_tot->rx_bytes = this_tot->vf_rx_bytes;
> + this_tot->tx_bytes = this_tot->vf_tx_bytes;
> + }
> +
> + /* fetch percpu stats of netvsc */
> + for (i = 0; i < nvdev->num_chn; i++) {
> + const struct netvsc_channel *nvchan = &nvdev->chan_table[i];
> + const struct netvsc_stats *stats;
> + struct netvsc_ethtool_pcpu_stats *this_tot =
> + per_cpu_ptr(pcpu_tot, nvchan->channel->target_cpu);
> + u64 packets, bytes;
> + unsigned int start;
> +
> + stats = &nvchan->tx_stats;
> + do {
> + start = u64_stats_fetch_begin_irq(&stats->syncp);
> + packets = stats->packets;
> + bytes = stats->bytes;
> + } while (u64_stats_fetch_retry_irq(&stats->syncp, start));
> +
> + this_tot->tx_bytes += bytes;
> + this_tot->tx_packets += packets;
> +
> + stats = &nvchan->rx_stats;
> + do {
> + start = u64_stats_fetch_begin_irq(&stats->syncp);
> + packets = stats->packets;
> + bytes = stats->bytes;
> + } while (u64_stats_fetch_retry_irq(&stats->syncp, start));
> +
> + this_tot->rx_bytes += bytes;
> + this_tot->rx_packets += packets;
> + }
> +}
> +
> static void netvsc_get_stats64(struct net_device *net,
> struct rtnl_link_stats64 *t)
> {
> @@ -1202,6 +1262,23 @@ static const struct {
> { "rx_no_memory", offsetof(struct netvsc_ethtool_stats, rx_no_memory) },
> { "stop_queue", offsetof(struct netvsc_ethtool_stats, stop_queue) },
> { "wake_queue", offsetof(struct netvsc_ethtool_stats, wake_queue) },
> +}, pcpu_stats[] = {
> + { "cpu%u_rx_packets",
> + offsetof(struct netvsc_ethtool_pcpu_stats, rx_packets) },
> + { "cpu%u_rx_bytes",
> + offsetof(struct netvsc_ethtool_pcpu_stats, rx_bytes) },
> + { "cpu%u_tx_packets",
> + offsetof(struct netvsc_ethtool_pcpu_stats, tx_packets) },
> + { "cpu%u_tx_bytes",
> + offsetof(struct netvsc_ethtool_pcpu_stats, tx_bytes) },
> + { "cpu%u_vf_rx_packets",
> + offsetof(struct netvsc_ethtool_pcpu_stats, vf_rx_packets) },
> + { "cpu%u_vf_rx_bytes",
> + offsetof(struct netvsc_ethtool_pcpu_stats, vf_rx_bytes) },
> + { "cpu%u_vf_tx_packets",
> + offsetof(struct netvsc_ethtool_pcpu_stats, vf_tx_packets) },
> + { "cpu%u_vf_tx_bytes",
> + offsetof(struct netvsc_ethtool_pcpu_stats, vf_tx_bytes) },
> }, vf_stats[] = {
> { "vf_rx_packets", offsetof(struct netvsc_vf_pcpu_stats, rx_packets) },
> { "vf_rx_bytes", offsetof(struct netvsc_vf_pcpu_stats, rx_bytes) },
> @@ -1213,6 +1290,9 @@ static const struct {
> #define NETVSC_GLOBAL_STATS_LEN ARRAY_SIZE(netvsc_stats)
> #define NETVSC_VF_STATS_LEN ARRAY_SIZE(vf_stats)
>
> +/* statistics per queue (rx/tx packets/bytes) */
> +#define NETVSC_PCPU_STATS_LEN (num_present_cpus() * ARRAY_SIZE(pcpu_stats))

Even though Hyper-V/Azure does not support hot plug cpu's it might be better
to num_cpu_possible to avoid any possible future surprises.