netdev - Re: [PATCH v2 net-next 21/26] ice: add XDP and XSK generic per-channel statistics

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Message-ID: <20211129070350.751e2afe@kicinski-fedora-pc1c0hjn.dhcp.thefacebook.com>
Date:   Mon, 29 Nov 2021 07:03:50 -0800
From:   Jakub Kicinski <kuba@...nel.org>
To:     Jesper Dangaard Brouer <jbrouer@...hat.com>
Cc:     Daniel Borkmann <daniel@...earbox.net>,
        Toke Høiland-Jørgensen 
        <toke@...hat.com>, brouer@...hat.com,
        Alexander Lobakin <alexandr.lobakin@...el.com>,
        "David S. Miller" <davem@...emloft.net>,
        Jesse Brandeburg <jesse.brandeburg@...el.com>,
        Michal Swiatkowski <michal.swiatkowski@...ux.intel.com>,
        Maciej Fijalkowski <maciej.fijalkowski@...el.com>,
        Jonathan Corbet <corbet@....net>,
        Shay Agroskin <shayagr@...zon.com>,
        Arthur Kiyanovski <akiyano@...zon.com>,
        David Arinzon <darinzon@...zon.com>,
        Noam Dagan <ndagan@...zon.com>,
        Saeed Bishara <saeedb@...zon.com>,
        Ioana Ciornei <ioana.ciornei@....com>,
        Claudiu Manoil <claudiu.manoil@....com>,
        Tony Nguyen <anthony.l.nguyen@...el.com>,
        Thomas Petazzoni <thomas.petazzoni@...tlin.com>,
        Marcin Wojtas <mw@...ihalf.com>,
        Russell King <linux@...linux.org.uk>,
        Saeed Mahameed <saeedm@...dia.com>,
        Leon Romanovsky <leon@...nel.org>,
        Alexei Starovoitov <ast@...nel.org>,
        Jesper Dangaard Brouer <hawk@...nel.org>,
        John Fastabend <john.fastabend@...il.com>,
        Edward Cree <ecree.xilinx@...il.com>,
        Martin Habets <habetsm.xilinx@...il.com>,
        "Michael S. Tsirkin" <mst@...hat.com>,
        Jason Wang <jasowang@...hat.com>,
        Andrii Nakryiko <andrii@...nel.org>,
        Martin KaFai Lau <kafai@...com>,
        Song Liu <songliubraving@...com>, Yonghong Song <yhs@...com>,
        KP Singh <kpsingh@...nel.org>,
        Lorenzo Bianconi <lorenzo@...nel.org>,
        Yajun Deng <yajun.deng@...ux.dev>,
        Sergey Ryazanov <ryazanov.s.a@...il.com>,
        David Ahern <dsahern@...nel.org>,
        Andrei Vagin <avagin@...il.com>,
        Johannes Berg <johannes.berg@...el.com>,
        Vladimir Oltean <vladimir.oltean@....com>,
        Cong Wang <cong.wang@...edance.com>, netdev@...r.kernel.org,
        linux-doc@...r.kernel.org, linux-kernel@...r.kernel.org,
        linux-rdma@...r.kernel.org, bpf@...r.kernel.org,
        Paolo Abeni <pabeni@...hat.com>
Subject: Re: [PATCH v2 net-next 21/26] ice: add XDP and XSK generic
 per-channel statistics

On Mon, 29 Nov 2021 14:59:53 +0100 Jesper Dangaard Brouer wrote:
> Hmm... I don't agree here.  IMHO the BPF-program's *choice* to drop (via 
> XDP_DROP) should NOT share the counter with the driver-related drops.
> 
> The driver-related drops must be accounted separate.

+1 FWIW. The Tx stat is a little misleading because it differs from the
definition of our other tx stats which mean _successfully_ transmitted
(and are accounted on the completion path in many drivers).

In the past I've used act_*, e.g. act_tx, to indicate the stat counts
returned actions, not whether the packet made it.

I still wonder whether it makes sense to count the stats per-action or
just have one "XDP consumed it" stat and that's it. The semantics of the
action are not of interest to the admin. A firewall can drop or tx
depending if it wants to send an ICMP reject or TCP RST message in
response. I need to know what the application does to understand the
difference, and if I do I can as well look at app stats. But I'm aware
I'm not going to find much support for this position, so just saying...
;)