netdev - Re: consistency for statistics with XDP mode

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Date:   Wed, 28 Nov 2018 12:03:45 +0800
From:   Jason Wang <jasowang@...hat.com>
To:     Toshiaki Makita <makita.toshiaki@....ntt.co.jp>,
        David Ahern <dsahern@...il.com>,
        "netdev@...r.kernel.org" <netdev@...r.kernel.org>
Cc:     Paweł Staszewski <pstaszewski@...are.pl>,
        Jesper Dangaard Brouer <brouer@...hat.com>,
        Saeed Mahameed <saeedm@...lanox.com>,
        "Michael S. Tsirkin" <mst@...hat.com>,
        David Miller <davem@...emloft.net>
Subject: Re: consistency for statistics with XDP mode


On 2018/11/27 下午3:04, Toshiaki Makita wrote:
> On 2018/11/26 10:37, Toshiaki Makita wrote:
>> On 2018/11/23 1:43, David Ahern wrote:
>>> On 11/21/18 5:53 PM, Toshiaki Makita wrote:
>>>>> We really need consistency in the counters and at a minimum, users
>>>>> should be able to track packet and byte counters for both Rx and Tx
>>>>> including XDP.
>>>>>
>>>>> It seems to me the Rx and Tx packet, byte and dropped counters returned
>>>>> for the standard device stats (/proc/net/dev, ip -s li show, ...) should
>>>>> include all packets managed by the driver regardless of whether they are
>>>>> forwarded / dropped in XDP or go up the Linux stack. This also aligns
>>>> Agreed. When I introduced virtio_net XDP counters, I just forgot to
>>>> update tx packets/bytes counters on ndo_xdp_xmit. Probably I thought it
>>>> is handled by free_old_xmit_skbs.
>>> Do you have some time to look at adding the Tx counters to virtio_net?
>> hoping I can make some time within a couple of days.
> Hmm... It looks like free_old_xmit_skbs() calls dev_consume_skb_any()
> for xdp_frame when napi_tx is enabled. I will fix this beforehand.


Good catch. But the fix may require some thought. E.g one idea is to not 
call free_old_xmit_skbs() for XDP TX ring?

Thanks