netdev - RE: [PATCH v6 net-next 3/4] net: ena: Add PHC documentation

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Message-ID: <796881fe22cc4129b69eadad7ff37a8b@amazon.com>
Date: Tue, 11 Feb 2025 06:41:27 +0000
From: "Arinzon, David" <darinzon@...zon.com>
To: Jakub Kicinski <kuba@...nel.org>
CC: David Miller <davem@...emloft.net>, "netdev@...r.kernel.org"
	<netdev@...r.kernel.org>, Eric Dumazet <edumazet@...gle.com>, Paolo Abeni
	<pabeni@...hat.com>, Simon Horman <horms@...nel.org>, Richard Cochran
	<richardcochran@...il.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>, "Schmeilin, Evgeny" <evgenys@...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>, "Bernstein, Amit"
	<amitbern@...zon.com>, "Agroskin, Shay" <shayagr@...zon.com>, "Abboud, Osama"
	<osamaabb@...zon.com>, "Ostrovsky, Evgeny" <evostrov@...zon.com>, "Tabachnik,
 Ofir" <ofirt@...zon.com>, "Machnikowski, Maciek" <maciek@...hnikowski.net>,
	Rahul Rameshbabu <rrameshbabu@...dia.com>, Gal Pressman <gal@...dia.com>
Subject: RE: [PATCH v6 net-next 3/4] net: ena: Add PHC documentation

> > You are right in the regard that it is not a network specific functionality.
> > Having said that, PHC is a network card capability, making it a network-
> related component rather than purely a timekeeping feature.
> > Moreover we failed to find an existing tool which would allow users to get
> valuable feedback of the system's overall health.
> >
> > Researching its existing support in the kernel we noted that:
> > - PHC is embedded in network NIC and is supported by multiple NIC
> > vendors in the kernel
> > - PHC information is visible through ethtool -T
> > - The Linux networking stack uses PHC for timekeeping as well as for packet
> timestamping (via SO_TIMESTAMPING).
> >   Packet timestamping statistics are available through ethtool
> > get_ts_stats hook
> >
> > We have found `ethtool -S` as a suitable location for exposing these
> statistics, which are unique to the ENA NIC.
> >
> > We'd appreciate your thoughts on the matter, is there an alternative tool
> you can recommend?
> 
> We try to steer folks towards read-only debugfs files for stuff that's not
> strictly networking related. You also add a custom sysfs file in patch 4, I
> reckon adding stats there may also be a natural place for the user?
> 
> Patch 4 FWIW is lacking slightly in the justification, would be good to clarify
> why it's disabled by default. Single sentence of "why" would be great.

Hi Jakub,

Thank you for the feedback and the recommendations, we will incorporate them in v7.