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From: David Ahern <dsahern@gmail.com>
To: Jakub Kicinski <kuba@kernel.org>, Saeed Mahameed <saeed@kernel.org>
Cc: Alexander Lobakin <alexandr.lobakin@intel.com>,
	"David S. Miller" <davem@davemloft.net>,
	Jesse Brandeburg <jesse.brandeburg@intel.com>,
	Lukasz Czapnik <lukasz.czapnik@intel.com>,
	Marcin Kubiak <marcin.kubiak@intel.com>,
	Michal Kubiak <michal.kubiak@intel.com>,
	Michal Swiatkowski <michal.swiatkowski@intel.com>,
	Jonathan Corbet <corbet@lwn.net>,
	Netanel Belgazal <netanel@amazon.com>,
	Arthur Kiyanovski <akiyano@amazon.com>,
	Guy Tzalik <gtzalik@amazon.com>,
	Saeed Bishara <saeedb@amazon.com>,
	Ioana Ciornei <ioana.ciornei@nxp.com>,
	Claudiu Manoil <claudiu.manoil@nxp.com>,
	Thomas Petazzoni <thomas.petazzoni@bootlin.com>,
	Marcin Wojtas <mw@semihalf.com>,
	Russell King <linux@armlinux.org.uk>,
	Edward Cree <ecree.xilinx@gmail.com>,
	Martin Habets <habetsm.xilinx@gmail.com>,
	"Michael S. Tsirkin" <mst@redhat.com>,
	Jason Wang <jasowang@redhat.com>,
	Alexei Starovoitov <ast@kernel.org>,
	Daniel Borkmann <daniel@iogearbox.net>,
	Jesper Dangaard Brouer <hawk@kernel.org>,
	John Fastabend <john.fastabend@gmail.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>,
	Shay Agroskin <shayagr@amazon.com>,
	Sameeh Jubran <sameehj@amazon.com>,
	Alexander Duyck <alexanderduyck@fb.com>,
	Danielle Ratson <danieller@nvidia.com>,
	Ido Schimmel <idosch@nvidia.com>, Andrew Lunn <andrew@lunn.ch>,
	Vladyslav Tarasiuk <vladyslavt@nvidia.com>,
	Arnd Bergmann <arnd@arndb.de>,
	Andrew Morton <akpm@linux-foundation.org>,
	Jian Shen <shenjian15@huawei.com>,
	Petr Vorel <petr.vorel@gmail.com>, Dan Murphy <dmurphy@ti.com>,
	Yangbo Lu <yangbo.lu@nxp.com>, Michal Kubecek <mkubecek@suse.cz>,
	Zheng Yongjun <zhengyongjun3@huawei.com>,
	Heiner Kallweit <hkallweit1@gmail.com>,
	YueHaibing <yuehaibing@huawei.com>,
	Johannes Berg <johannes@sipsolutions.net>,
	netdev@vger.kernel.org, linux-doc@vger.kernel.org,
	linux-kernel@vger.kernel.org,
	virtualization@lists.linux-foundation.org, bpf@vger.kernel.org
Subject: Re: [PATCH net-next 03/21] ethtool, stats: introduce standard XDP statistics
Date: Wed, 4 Aug 2021 10:17:56 -0600	[thread overview]
Message-ID: <43e91ce1-0f82-5820-7cac-b42461a0311a@gmail.com> (raw)
In-Reply-To: <20210804053650.22aa8a5b@kicinski-fedora-pc1c0hjn.dhcp.thefacebook.com>

On 8/4/21 6:36 AM, Jakub Kicinski wrote:
>> XDP is going to always be eBPF based ! why not just report such stats
>> to a special BPF_MAP ? BPF stack can collect the stats from the driver
>> and report them to this special MAP upon user request.
> Do you mean replacing the ethtool-netlink / rtnetlink etc. with
> a new BPF_MAP? I don't think adding another category of uAPI thru 
> which netdevice stats are exposed would do much good :( Plus it 
> doesn't address the "yet another cacheline" concern.
> 
> To my understanding the need for stats recognizes the fact that (in
> large organizations) fleet monitoring is done by different teams than
> XDP development. So XDP team may have all the stats they need, but the
> team doing fleet monitoring has no idea how to get to them.
> 
> To bridge the two worlds we need a way for the infra team to ask the
> XDP for well-defined stats. Maybe we should take a page from the BPF
> iterators book and create a program type for bridging the two worlds?
> Called by networking core when duping stats to extract from the
> existing BPF maps all the relevant stats and render them into a well
> known struct? Users' XDP design can still use a single per-cpu map with
> all the stats if they so choose, but there's a way to implement more
> optimal designs and still expose well-defined stats.
> 
> Maybe that's too complex, IDK.

I was just explaining to someone internally how to get stats at all of
the different points in the stack to track down reasons for dropped packets:

ethtool -S for h/w and driver
tc -s for drops by the qdisc
/proc/net/softnet_stat for drops at the backlog layer
netstat -s for network and transport layer

yet another command and API just adds to the nightmare of explaining and
understanding these stats.

There is real value in continuing to use ethtool API for XDP stats. Not
saying this reorg of the XDP stats is the right thing to do, only that
the existing API has real user benefits.

Does anyone have data that shows bumping a properly implemented counter
causes a noticeable performance degradation and if so by how much? You
mention 'yet another cacheline' but collecting stats on stack and
incrementing the driver structs at the end of the napi loop should not
have a huge impact versus the value the stats provide.

  parent reply	other threads:[~2021-08-04 16:18 UTC|newest]

Thread overview: 45+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2021-08-03 16:36 [PATCH net-next 00/21] ethtool, stats: introduce and use standard XDP stats Alexander Lobakin
2021-08-03 16:36 ` [PATCH net-next 01/21] ethtool, stats: use a shorthand pointer in stats_prepare_data() Alexander Lobakin
2021-08-03 16:36 ` [PATCH net-next 02/21] ethtool, stats: add compile-time checks for standard stats Alexander Lobakin
2021-08-03 16:36 ` [PATCH net-next 03/21] ethtool, stats: introduce standard XDP statistics Alexander Lobakin
2021-08-03 20:49   ` Jakub Kicinski
2021-08-03 23:57     ` Saeed Mahameed
2021-08-04 12:36       ` Jakub Kicinski
2021-08-04 15:53         ` Alexander Lobakin
2021-08-04 16:57           ` Jakub Kicinski
2021-08-05 11:18             ` Alexander Lobakin
2021-08-05 13:31               ` Jakub Kicinski
2021-08-04 16:17         ` David Ahern [this message]
2021-08-04 16:44           ` Jakub Kicinski
2021-08-04 17:28             ` David Ahern
2021-08-04 18:27               ` Saeed Mahameed
2021-08-05  0:43                 ` David Ahern
2021-08-05  2:14                   ` Saeed Mahameed
2021-08-12 12:19             ` Jesper Dangaard Brouer
2021-10-26  9:23       ` Alexander Lobakin
2021-11-05 16:44         ` Alexander Lobakin
2021-11-08 11:37           ` Toke Høiland-Jørgensen
2021-11-08 13:21             ` Alexander Lobakin
2021-11-08 18:09               ` Toke Høiland-Jørgensen
2021-08-03 16:36 ` [PATCH net-next 04/21] ethernet, dpaa2: simplify per-channel Ethtool stats counting Alexander Lobakin
2021-08-03 16:36 ` [PATCH net-next 05/21] ethernet, dpaa2: convert to standard XDP stats Alexander Lobakin
2021-08-03 16:36 ` [PATCH net-next 06/21] ethernet, ena: constify src and syncp args of ena_safe_update_stat() Alexander Lobakin
2021-08-03 16:36 ` [PATCH net-next 07/21] ethernet, ena: convert to standard XDP stats Alexander Lobakin
2021-08-04 13:04   ` Shay Agroskin
2021-08-04 15:24     ` Alexander Lobakin
2021-08-03 16:36 ` [PATCH net-next 08/21] ethernet, enetc: " Alexander Lobakin
2021-08-03 16:36 ` [PATCH net-next 09/21] ethernet, mvneta: rename xdp_xmit_err to xdp_xmit_drops Alexander Lobakin
2021-08-03 16:36 ` [PATCH net-next 10/21] ethernet, mvneta: convert to standard XDP stats Alexander Lobakin
2021-08-03 16:36 ` [PATCH net-next 11/21] ethernet, mvpp2: rename xdp_xmit_err to xdp_xmit_drops Alexander Lobakin
2021-08-03 16:36 ` [PATCH net-next 12/21] ethernet, mvpp2: convert to standard XDP stats Alexander Lobakin
2021-08-03 16:36 ` [PATCH net-next 13/21] ethernet, sfc: " Alexander Lobakin
2021-08-03 17:59   ` Edward Cree
2021-08-03 16:36 ` [PATCH net-next 14/21] veth: rename rx_drops to xdp_errors Alexander Lobakin
2021-08-03 16:36 ` [PATCH net-next 15/21] veth: rename xdp_xmit_errors to xdp_xmit_drops Alexander Lobakin
2021-08-03 16:36 ` [PATCH net-next 16/21] veth: rename drop xdp_ suffix from packets and bytes stats Alexander Lobakin
2021-08-03 16:36 ` [PATCH net-next 17/21] veth: convert to standard XDP stats Alexander Lobakin
2021-08-03 16:36 ` [PATCH net-next 18/21] virtio-net: rename xdp_tx{,__drops} SQ stats to xdp_xmit{,__drops} Alexander Lobakin
2021-08-03 16:42 ` Alexander Lobakin
2021-08-03 16:42 ` [PATCH net-next 19/21] virtio-net: don't mix error-caused drops with XDP_DROP cases Alexander Lobakin
2021-08-03 16:42 ` [PATCH net-next 20/21] virtio-net: convert to standard XDP stats Alexander Lobakin
2021-08-03 16:42 ` [PATCH net-next 21/21] Documentation, ethtool-netlink: update standard statistics documentation Alexander Lobakin

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