linux-kernel - Re: [PATCH net-next v4 2/2] net: xilinx: axienet: Add statistics support

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Message-ID: <98441cee-193d-404c-8dc5-9cf2061ce2e4@lunn.ch>
Date: Tue, 20 Aug 2024 22:23:12 +0200
From: Andrew Lunn <andrew@...n.ch>
To: Sean Anderson <sean.anderson@...ux.dev>
Cc: "Pandey, Radhey Shyam" <radhey.shyam.pandey@....com>,
	"netdev@...r.kernel.org" <netdev@...r.kernel.org>,
	"Simek, Michal" <michal.simek@....com>,
	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
	Russell King <linux@...linux.org.uk>,
	"David S . Miller" <davem@...emloft.net>,
	Jakub Kicinski <kuba@...nel.org>, Paolo Abeni <pabeni@...hat.com>,
	Eric Dumazet <edumazet@...gle.com>, Simon Horman <horms@...nel.org>,
	"linux-arm-kernel@...ts.infradead.org" <linux-arm-kernel@...ts.infradead.org>,
	"Katakam, Harini" <harini.katakam@....com>
Subject: Re: [PATCH net-next v4 2/2] net: xilinx: axienet: Add statistics
 support

> > Is that a standard convention to retain/persist counter values across 
> > link up/down?
> 
> IEEE 802.3 section 30.2.1 says
> 
> | All counters defined in this specification are assumed to be
> | wrap-around counters. Wrap-around counters are those that
> | automatically go from their maximum value (or final value) to zero and
> | continue to operate. These unsigned counters do not provide for any
> | explicit means to return them to their minimum (zero), i.e., reset.
> 
> And get_eth_mac_stats implements these counters for Linux. So I would
> say that resetting the counters on link up/down would be non-conformant.
> 
> Other drivers also preserve stats across link up/down. For example,
> MACB/GEM doesn't reset it stats either. And keeping the stats is also
> more friendly for users and monitoring tools.

Agreed.

Some driver get this wrong, and clear them. But as a reviewer, it try
to spot this.

   Andrew