netdev - RE: [PATCH v1 net-next 2/2] net: ena: Extend customer metrics reporting support

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Message-ID: <686a380af2774aa9ade5a9baa1f9e49a@amazon.com>
Date: Tue, 3 Sep 2024 04:29:18 +0000
From: "Arinzon, David" <darinzon@...zon.com>
To: Parav Pandit <parav@...dia.com>, Jakub Kicinski <kuba@...nel.org>, "Xuan
 Zhuo" <xuanzhuo@...ux.alibaba.com>, "Michael S. Tsirkin" <mst@...hat.com>
CC: David Miller <davem@...emloft.net>, "netdev@...r.kernel.org"
	<netdev@...r.kernel.org>, Eric Dumazet <edumazet@...gle.com>, Paolo Abeni
	<pabeni@...hat.com>, "Woodhouse, David" <dwmw@...zon.co.uk>, "Machulsky,
 Zorik" <zorik@...zon.com>, "Matushevsky, Alexander" <matua@...zon.com>,
	"Bshara, Saeed" <saeedb@...zon.com>, "Wilson, Matt" <msw@...zon.com>,
	"Liguori, Anthony" <aliguori@...zon.com>, "Bshara, Nafea" <nafea@...zon.com>,
	"Belgazal, Netanel" <netanel@...zon.com>, "Saidi, Ali" <alisaidi@...zon.com>,
	"Herrenschmidt, Benjamin" <benh@...zon.com>, "Kiyanovski, Arthur"
	<akiyano@...zon.com>, "Dagan, Noam" <ndagan@...zon.com>, "Agroskin, Shay"
	<shayagr@...zon.com>, "Itzko, Shahar" <itzko@...zon.com>, "Abboud, Osama"
	<osamaabb@...zon.com>, "Ostrovsky, Evgeny" <evostrov@...zon.com>, "Tabachnik,
 Ofir" <ofirt@...zon.com>, "Beider, Ron" <rbeider@...zon.com>, "Chauskin,
 Igor" <igorch@...zon.com>, "Bernstein, Amit" <amitbern@...zon.com>, "Cornelia
 Huck" <cohuck@...hat.com>
Subject: RE: [PATCH v1 net-next 2/2] net: ena: Extend customer metrics reporting
 support

> > > I've looked into the definition of the metrics under question
> > >
> > > Based on AWS documentation
> > > (https://docs.aws.amazon.com/AWSEC2/latest/UserGuide/monitoring-
> > networ
> > > k-performance-ena.html)
> > >
> > > bw_in_allowance_exceeded: The number of packets queued or dropped
> > because the inbound aggregate bandwidth exceeded the maximum for the
> > instance.
> > > bw_out_allowance_exceeded: The number of packets queued or
> dropped
> > because the outbound aggregate bandwidth exceeded the maximum for
> the
> > instance.
> > >
> > > Based on the netlink spec
> > > (https://docs.kernel.org/next/networking/netlink_spec/netdev.html)
> > >
> > > rx-hw-drop-ratelimits (uint)
> > > doc: Number of the packets dropped by the device due to the received
> > packets bitrate exceeding the device rate limit.
> > > tx-hw-drop-ratelimits (uint)
> > > doc: Number of the packets dropped by the device due to the transmit
> > packets bitrate exceeding the device rate limit.
> > >
> > > The AWS metrics are counting for packets dropped or queued (delayed,
> > > but
> > are sent/received with a delay), a change in these metrics is an
> > indication to customers to check their applications and workloads due
> > to risk of exceeding limits.
> > > There's no distinction between dropped and queued in these metrics,
> > therefore, they do not match the ratelimits in the netlink spec.
> > > In case there will be a separation of these metrics in the future to
> > > dropped
> > and queued, we'll be able to add the support for hw-drop-ratelimits.
> >
> > Xuan, Michael, the virtio spec calls out drops due to b/w limit being
> > exceeded, but AWS people say their NICs also count packets buffered
> > but not dropped towards a similar metric.
> >
> > I presume the virtio spec is supposed to cover the same use cases.
> On tx side, number of packets may not be queued, but may not be even
> DMAed if the rate has exceeded.
> This is hw nic implementation detail and a choice with trade-offs.
> 
> Similarly on rx, one may implement drop or queue or both (queue upto some
> limit, and drop beyond it).
> 
> > Have the stats been approved?
> Yes. it is approved last year; I have also reviewed it; It is part of the spec
> nearly 10 months ago at [1].
> GH PR is merged but GH is not updated yet.
> 
> [1] https://github.com/oasis-tcs/virtio-
> spec/commit/42f389989823039724f95bbbd243291ab0064f82
> 
> > Is it reasonable to extend the definition of the "exceeded" stats in
> > the virtio spec to cover what AWS specifies?
> Virtio may add new stats for exceeded stats in future.
> But I do not understand how AWS ENA nic is related to virtio PCI HW nic.
> 
> Should virtio implement it? may be yes. Looks useful to me.
> Should it be now in virtio spec, not sure, this depends on virtio community
> and actual hw/sw supporting it.
> 
> > Looks like PR is still open:
> > https://github.com/oasis-tcs/virtio-spec/issues/180
> Spec already has it at [1] for drops. GH PR is not upto date.

Thank you for the reply, Parav.
I've raised the query and the summary of this discussion in the above mentioned github ticket.