Date:   Thu, 26 Apr 2018 15:37:29 -0700
From:   Qing Huang <qing.huang@...cle.com>
To:     Saeed Mahameed <saeedm@....mellanox.co.il>,
        Eran Ben Elisha <eranbe@...lanox.com>
Cc:     linux-kernel <linux-kernel@...r.kernel.org>,
        RDMA mailing list <linux-rdma@...r.kernel.org>,
        Linux Netdev List <netdev@...r.kernel.org>,
        Leon Romanovsky <leon@...nel.org>,
        Matan Barak <matanb@...lanox.com>,
        Saeed Mahameed <saeedm@...lanox.com>
Subject: Re: [PATCH] net/mlx5: report persistent netdev stats across
 ifdown/ifup commands



On 04/26/2018 02:50 PM, Saeed Mahameed wrote:
> On Thu, Apr 26, 2018 at 1:37 PM, Qing Huang <qing.huang@...cle.com> wrote:
>> Current stats collecting scheme in mlx5 driver is to periodically fetch
>> aggregated stats from all the active mlx5 software channels associated
>> with the device. However when a mlx5 interface is brought down(ifdown),
>> all the channels will be deactivated and closed. A new set of channels
>> will be created when next ifup command or a similar command is called.
>> Unfortunately the new channels will have all stats reset to 0. So you
>> lose the accumulated stats information. This behavior is different from
>> other netdev drivers including the mlx4 driver. In order to fix it, we
>> now save prior mlx5 software stats into netdev stats fields, so all the
>> accumulated stats will survive multiple runs of ifdown/ifup commands and
>> be shown correctly.
>>
>> Orabug: 27548610
>>
>> Signed-off-by: Qing Huang <qing.huang@...cle.com>
>> ---
> Hi Qing,
>
> I am adding Eran since he is currently working on a similar patch,
> He is also taking care of all cores/rings stats to make them
> persistent, so you won't have discrepancy  between
> ethtool and ifconfig stats.
>
> I am ok with this patch, but this means Eran has to work his way around it.
>
> so we have two options:
>
> 1. Temporary accept this patch, and change it later with Eran's work.
> 2. Wait for Eran's work.
>
> I am ok with either one of them, please let me know.
>
> Thanks !
Hi Saeed,

Any idea on rough ETA of Eran's stats work to be in upstream? If it will 
be available soon, I think
we can wait a bit. If it will take a while to redesign the whole stats 
scheme (for both ethtool and ifconfig),
maybe we can go with this incremental fix first?

Thanks!

>
>>   drivers/net/ethernet/mellanox/mlx5/core/en_main.c | 30 +++++++++++++++++++----
>>   1 file changed, 25 insertions(+), 5 deletions(-)
>>
>> diff --git a/drivers/net/ethernet/mellanox/mlx5/core/en_main.c b/drivers/net/ethernet/mellanox/mlx5/core/en_main.c
>> index f1fe490..5d50e69 100644
>> --- a/drivers/net/ethernet/mellanox/mlx5/core/en_main.c
>> +++ b/drivers/net/ethernet/mellanox/mlx5/core/en_main.c
>> @@ -2621,6 +2621,23 @@ static void mlx5e_netdev_set_tcs(struct net_device *netdev)
>>                  netdev_set_tc_queue(netdev, tc, nch, 0);
>>   }
>>
>> +static void mlx5e_netdev_save_stats(struct mlx5e_priv *priv)
>> +{
>> +       struct net_device *netdev = priv->netdev;
>> +
>> +       netdev->stats.rx_packets += priv->stats.sw.rx_packets;
>> +       netdev->stats.rx_bytes   += priv->stats.sw.rx_bytes;
>> +       netdev->stats.tx_packets += priv->stats.sw.tx_packets;
>> +       netdev->stats.tx_bytes   += priv->stats.sw.tx_bytes;
>> +       netdev->stats.tx_dropped += priv->stats.sw.tx_queue_dropped;
>> +
>> +       priv->stats.sw.rx_packets       = 0;
>> +       priv->stats.sw.rx_bytes         = 0;
>> +       priv->stats.sw.tx_packets       = 0;
>> +       priv->stats.sw.tx_bytes         = 0;
>> +       priv->stats.sw.tx_queue_dropped = 0;
>> +}
>> +
> This means that we are now explicitly clearing channels stats on
> ifconfig down or switch_channels.
> and now after ifconfing down, ethtool will always show 0, before this
> patch it didn't.
> Anyway update sw stats function will always override them with the new
> channels stats next time we load new channels.
> so it is not that big of a deal.
>
>
>>   static void mlx5e_build_channels_tx_maps(struct mlx5e_priv *priv)
>>   {
>>          struct mlx5e_channel *c;
>> @@ -2691,6 +2708,7 @@ void mlx5e_switch_priv_channels(struct mlx5e_priv *priv,
>>                  netif_set_real_num_tx_queues(netdev, new_num_txqs);
>>
>>          mlx5e_deactivate_priv_channels(priv);
>> +       mlx5e_netdev_save_stats(priv);
>>          mlx5e_close_channels(&priv->channels);
>>
>>          priv->channels = *new_chs;
>> @@ -2770,6 +2788,7 @@ int mlx5e_close_locked(struct net_device *netdev)
>>
>>          netif_carrier_off(priv->netdev);
>>          mlx5e_deactivate_priv_channels(priv);
>> +       mlx5e_netdev_save_stats(priv);
>>          mlx5e_close_channels(&priv->channels);
>>
>>          return 0;
>> @@ -3215,11 +3234,12 @@ static int mlx5e_setup_tc(struct net_device *dev, enum tc_setup_type type,
>>                  stats->tx_packets = PPORT_802_3_GET(pstats, a_frames_transmitted_ok);
>>                  stats->tx_bytes   = PPORT_802_3_GET(pstats, a_octets_transmitted_ok);
>>          } else {
>> -               stats->rx_packets = sstats->rx_packets;
>> -               stats->rx_bytes   = sstats->rx_bytes;
>> -               stats->tx_packets = sstats->tx_packets;
>> -               stats->tx_bytes   = sstats->tx_bytes;
>> -               stats->tx_dropped = sstats->tx_queue_dropped;
>> +               stats->rx_packets = sstats->rx_packets + dev->stats.rx_packets;
>> +               stats->rx_bytes   = sstats->rx_bytes + dev->stats.rx_bytes;
>> +               stats->tx_packets = sstats->tx_packets + dev->stats.tx_packets;
>> +               stats->tx_bytes   = sstats->tx_bytes + dev->stats.tx_bytes;
>> +               stats->tx_dropped = sstats->tx_queue_dropped +
>> +                                   dev->stats.tx_dropped;
>>          }
>>
>>          stats->rx_dropped = priv->stats.qcnt.rx_out_of_buffer;
>> --
>> 1.8.3.1
>>

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