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

From: Jakub Kicinski <kuba@kernel.org>
To: "Toke Høiland-Jørgensen" <toke@redhat.com>
Cc: Alexander Lobakin <alexandr.lobakin@intel.com>,
	Daniel Borkmann <daniel@iogearbox.net>,
	"David S. Miller" <davem@davemloft.net>,
	Jesse Brandeburg <jesse.brandeburg@intel.com>,
	Michal Swiatkowski <michal.swiatkowski@linux.intel.com>,
	Maciej Fijalkowski <maciej.fijalkowski@intel.com>,
	Jonathan Corbet <corbet@lwn.net>,
	Shay Agroskin <shayagr@amazon.com>,
	Arthur Kiyanovski <akiyano@amazon.com>,
	David Arinzon <darinzon@amazon.com>,
	Noam Dagan <ndagan@amazon.com>, Saeed Bishara <saeedb@amazon.com>,
	Ioana Ciornei <ioana.ciornei@nxp.com>,
	Claudiu Manoil <claudiu.manoil@nxp.com>,
	Tony Nguyen <anthony.l.nguyen@intel.com>,
	Thomas Petazzoni <thomas.petazzoni@bootlin.com>,
	Marcin Wojtas <mw@semihalf.com>,
	Russell King <linux@armlinux.org.uk>,
	Saeed Mahameed <saeedm@nvidia.com>,
	Leon Romanovsky <leon@kernel.org>,
	Alexei Starovoitov <ast@kernel.org>,
	Jesper Dangaard Brouer <hawk@kernel.org>,
	John Fastabend <john.fastabend@gmail.com>,
	Edward Cree <ecree.xilinx@gmail.com>,
	Martin Habets <habetsm.xilinx@gmail.com>,
	"Michael S. Tsirkin" <mst@redhat.com>,
	Jason Wang <jasowang@redhat.com>,
	Andrii Nakryiko <andrii@kernel.org>,
	Martin KaFai Lau <kafai@fb.com>, Song Liu <songliubraving@fb.com>,
	Yonghong Song <yhs@fb.com>, KP Singh <kpsingh@kernel.org>,
	Lorenzo Bianconi <lorenzo@kernel.org>,
	Yajun Deng <yajun.deng@linux.dev>,
	Sergey Ryazanov <ryazanov.s.a@gmail.com>,
	David Ahern <dsahern@kernel.org>, Andrei Vagin <avagin@gmail.com>,
	Johannes Berg <johannes.berg@intel.com>,
	Vladimir Oltean <vladimir.oltean@nxp.com>,
	Cong Wang <cong.wang@bytedance.com>,
	netdev@vger.kernel.org, linux-doc@vger.kernel.org,
	linux-kernel@vger.kernel.org, linux-rdma@vger.kernel.org,
	bpf@vger.kernel.org, virtualization@lists.linux-foundation.org
Subject: Re: [PATCH v2 net-next 21/26] ice: add XDP and XSK generic per-channel statistics
Date: Fri, 26 Nov 2021 11:14:31 -0800	[thread overview]
Message-ID: <20211126111431.4a2ed007@kicinski-fedora-pc1c0hjn.dhcp.thefacebook.com> (raw)
In-Reply-To: <87ee72ah56.fsf@toke.dk>

On Fri, 26 Nov 2021 19:47:17 +0100 Toke Høiland-Jørgensen wrote:
> > Fair. In all honesty I said that hoping to push for a more flexible
> > approach hidden entirely in BPF, and not involving driver changes.
> > Assuming the XDP program has more fine grained stats we should be able
> > to extract those instead of double-counting. Hence my vague "let's work
> > with apps" comment.
> >
> > For example to a person familiar with the workload it'd be useful to
> > know if program returned XDP_DROP because of configured policy or
> > failure to parse a packet. I don't think that sort distinction is
> > achievable at the level of standard stats.
> >
> > The information required by the admin is higher level. As you say the
> > primary concern there is "how many packets did XDP eat".  
> 
> Right, sure, I am also totally fine with having only a somewhat
> restricted subset of stats available at the interface level and make
> everything else be BPF-based. I'm hoping we can converge of a common
> understanding of what this "minimal set" should be :)
> 
> > Speaking of which, one thing that badly needs clarification is our
> > expectation around XDP packets getting counted towards the interface
> > stats.  
> 
> Agreed. My immediate thought is that "XDP packets are interface packets"
> but that is certainly not what we do today, so not sure if changing it
> at this point would break things?

I'd vote for taking the risk and trying to align all the drivers.