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From:   Saeed Mahameed <saeedm@dev.mellanox.co.il>
Date:   Thu, 26 Apr 2018 16:30:52 -0700
Message-ID: <CALzJLG8atGxoJNQj4F6wR3kRg7jrj4oQi3O-1i0=UOo+3HPq0w@mail.gmail.com>
Subject: Re: [PATCH] net/mlx5: report persistent netdev stats across
 ifdown/ifup commands
To:     Qing Huang <qing.huang@oracle.com>
Cc:     Eran Ben Elisha <eranbe@mellanox.com>,
        linux-kernel <linux-kernel@vger.kernel.org>,
        RDMA mailing list <linux-rdma@vger.kernel.org>,
        Linux Netdev List <netdev@vger.kernel.org>,
        Leon Romanovsky <leon@kernel.org>,
        Matan Barak <matanb@mellanox.com>,
        Saeed Mahameed <saeedm@mellanox.com>
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On Thu, Apr 26, 2018 at 3:37 PM, Qing Huang <qing.huang@oracle.com> wrote:
>
>
> On 04/26/2018 02:50 PM, Saeed Mahameed wrote:
>>
>> On Thu, Apr 26, 2018 at 1:37 PM, Qing Huang <qing.huang@oracle.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

I don't think we need this internal bug reference, let's remove it.

>>>
>>> Signed-off-by: Qing Huang <qing.huang@oracle.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

All i know that it is planned for v4.18.

> 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?
>

Yes we can go with incremental fix,
but let's fix the commit message as requested above and make the patch
title prefix "net/mlx5e:"
since this is a mlx5 netdev related change, not mlx5/core.
also please see a comments below.

Thanks,
Saeed.

> 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;

Note: it is safe to do this here since writing to priv->stats.sw is
currently done under priv->state_lock,
Please add a comment to this function that it must be called under
priv->state_lock

>>> +}
>>> +
>>
>> 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);

This function call doesn't have to be between deactivate and close,
lets move it to after
mlx5e_close_channels here and below to avoid confusion.

also you need to accumulate what is left in the rings/channels stats,
before calling
mlx5e_close_channels, see mlx5e_grp_sw_update_stats.

>>>          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
>>>
>