netdev - Re: consistency for statistics with XDP mode

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Date:   Mon, 3 Dec 2018 08:45:12 -0700
From:   David Ahern <dsahern@...il.com>
To:     Jesper Dangaard Brouer <brouer@...hat.com>,
        Saeed Mahameed <saeedm@...lanox.com>
Cc:     "mst@...hat.com" <mst@...hat.com>, "toke@...e.dk" <toke@...e.dk>,
        "netdev@...r.kernel.org" <netdev@...r.kernel.org>,
        "pstaszewski@...are.pl" <pstaszewski@...are.pl>,
        "davem@...emloft.net" <davem@...emloft.net>,
        "jasowang@...hat.com" <jasowang@...hat.com>
Subject: Re: consistency for statistics with XDP mode

On 12/1/18 4:22 AM, Jesper Dangaard Brouer wrote:
>>
>> So we should count all XDP RX packets as successful rx packets i.e
>> netdev->stats.rx_packets++; regardless of the XDP program decision ? 
> 
> Yes.
> 
>> this implies that XDP_TX packets will be counted twice once in 
>> netdev->stats.rx_packets and once in netdev->stats.tx_packets
> 
> Yes, because the packet was RX'ed on the interface, and then TX'ed on
> the interface.  Users expect to see these packets (ac)counted.

+1

> 
>> I think this is the only valid option if we are going to use standard
>> netdev stats for XDP use cases.
> 
> IMHO XDP_DROP should not be accounted as netdev stats drops, this is a
> user installed program like tc/iptables, that can also choose to drop
> packets.
> 

sure and both tc and iptables have counters that can see the dropped
packets. A counter in the driver level stats ("xdp_drop" is fine with
with me).