netdev - Re: [PATCH net-next 2/2] net/mlx4_en: Refactor the XDP forwarding rings scheme

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Date:   Mon, 31 Oct 2016 01:11:34 +0200
From:   Saeed Mahameed <saeedm@....mellanox.co.il>
To:     Alexei Starovoitov <alexei.starovoitov@...il.com>
Cc:     Tariq Toukan <ttoukan.linux@...il.com>,
        Tariq Toukan <tariqt@...lanox.com>,
        "David S. Miller" <davem@...emloft.net>,
        Linux Netdev List <netdev@...r.kernel.org>,
        Eran Ben Elisha <eranbe@...lanox.com>,
        Brenden Blanco <bblanco@...mgrid.com>
Subject: Re: [PATCH net-next 2/2] net/mlx4_en: Refactor the XDP forwarding
 rings scheme

On Mon, Oct 31, 2016 at 12:44 AM, Alexei Starovoitov
<alexei.starovoitov@...il.com> wrote:
> On Sun, Oct 30, 2016 at 06:03:06PM +0200, Tariq Toukan wrote:
>>
>> Note that the XDP TX rings are no longer shown in ethtool -S.
>
> ouch. Can you make it to show them as some large TX numbers instead?
> It would really sux to lose stats on them.
>

Right, Tariq, how did we miss this ?

FYI, I don't think we need the whole TX queue stats for XDP tx rings,
it is just an overkill, there are only two active counters for XDP TX
ring (XDP_TX_FWD/XDP_TX_DROP).

XDP_TX_FWD or currently "tx_packets" will count successfully forwarded packets
XDP_TX_DROP or currently "tx_dropped" will count TX dropped packets
due to full ring.

do we need tx_bytes as well ? I think yes.

The whole idea of this refactoring i.e. differentiating between TXQ
netdev rings and XDP TX rings, that XDP is a fast path with minimal
system overhead, we don't need to have the full set of regular TXQ
counters for XDP TX rings.