netdev - Re: [PATCH v3 net-next 3/3] net: ena: Add PHC documentation

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Message-ID: <20241105181552.02ea5525@kernel.org>
Date: Tue, 5 Nov 2024 18:15:52 -0800
From: Jakub Kicinski <kuba@...nel.org>
To: Rahul Rameshbabu <rrameshbabu@...dia.com>
Cc: "Arinzon, David" <darinzon@...zon.com>, Gal Pressman <gal@...dia.com>,
 David Miller <davem@...emloft.net>, "netdev@...r.kernel.org"
 <netdev@...r.kernel.org>, Eric Dumazet <edumazet@...gle.com>, Paolo Abeni
 <pabeni@...hat.com>, 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>
Subject: Re: [PATCH v3 net-next 3/3] net: ena: Add PHC documentation

On Tue, 05 Nov 2024 18:02:57 -0800 Rahul Rameshbabu wrote:
> I do think the phc-to-host related statistics are on the niche side of
> things. The following drivers are error free in their gettimex64 paths.
> 
> * AMD pesando/ionic
> * Broadcom Tigon3
> * Intel ixgbe
> * Intel igc
> * NVIDIA mlxsw
> * NVIDIA mlx5_core
> 
> The above drivers would definitely not benefit from having "phc
> (nic)"-to-host related statistics being presented here. I am more in
> favor of making these statistics specific to amazon's ENA driver since I
> think most drivers do not have a complex . Also, what value is there in
> the count of phc-to-host successful/failed operations versus just
> keeping track of the errors in userspace for whoever is calling
> clock_gettime. I am somewhat ok with these counters, but I honestly
> cannot imagine any practical use to this especially since they are not
> related to anything over-the-wire. So the errors in userspace would be
> enough of an indicator of whether there is excessive utilization of the
> requests and the counters seem redundant to that (at least to me). Feel
> free to share how you feel these counters would be helpful beyond
> handling the return codes through clock_gettime. I might just be missing
> something.

Agreed, thanks a lot for the analysis. I misread the code.
I looked at ena_com_phc_get() last night and incorrectly 
assumed it's way to complex to be called from gettimex64 :S