linux-kernel - Re: [PATCH net-next v1 2/3] net: dsa: ar9331: add support for pause stats

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Message-ID: <20220628091027.3693f3f9@kernel.org>
Date:   Tue, 28 Jun 2022 09:10:27 -0700
From:   Jakub Kicinski <kuba@...nel.org>
To:     Oleksij Rempel <o.rempel@...gutronix.de>
Cc:     Andrew Lunn <andrew@...n.ch>,
        Woojung Huh <woojung.huh@...rochip.com>,
        Florian Fainelli <f.fainelli@...il.com>,
        netdev@...r.kernel.org, linux-kernel@...r.kernel.org,
        "David S. Miller" <davem@...emloft.net>,
        Eric Dumazet <edumazet@...gle.com>,
        Lukas Wunner <lukas@...ner.de>, kernel@...gutronix.de,
        Paolo Abeni <pabeni@...hat.com>,
        Vladimir Oltean <olteanv@...il.com>,
        Vivien Didelot <vivien.didelot@...il.com>,
        UNGLinuxDriver@...rochip.com
Subject: Re: [PATCH net-next v1 2/3] net: dsa: ar9331: add support for pause
 stats

On Tue, 28 Jun 2022 10:45:04 +0200 Oleksij Rempel wrote:
> After I started investigating this topic, I was really frustrated. It is
> has hard to find what is wrong: my patch is not working and flow
> controller is not triggered? Or every HW/driver implements counters in
> some own way. Same is about byte counts: for same packet with different
> NICs i have at least 3 different results: 50, 64 and 68.
> It makes testing and validation a nightmare. 

Yeah, I was gonna mention QA in my reply. The very practical reason I've
gone no-CRC, no-flow control in the driver stats in the past was that it
made it possible to test the counters are correct and the match far end.
I mean SW matches HW, and they both match between sender/receiver
(testing NIC-switch-NIC if either link does flow control the counters
on NICs won't match).