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[2003:ea:8f23:2800:8821:97f2:24b4:2f18]) by smtp.googlemail.com with ESMTPSA id me12sm7337365ejb.108.2020.10.18.06.09.37 (version=TLS1_3 cipher=TLS_AES_128_GCM_SHA256 bits=128/128); Sun, 18 Oct 2020 06:09:37 -0700 (PDT) Subject: Re: [RFC PATCH 01/13] net: dsa: add plumbing for custom netdev statistics To: Vladimir Oltean Cc: "netdev@vger.kernel.org" , "andrew@lunn.ch" , "f.fainelli@gmail.com" , "vivien.didelot@gmail.com" , "kuba@kernel.org" , Christian Eggers , Kurt Kanzenbach References: <20201017213611.2557565-1-vladimir.oltean@nxp.com> <20201017213611.2557565-2-vladimir.oltean@nxp.com> <06538edb-65a9-c27f-2335-9213322bed3a@gmail.com> <20201018121640.jwzj6ivpis4gh4ki@skbuf> From: Heiner Kallweit Message-ID: <19f10bf4-4154-2207-6554-e44ba05eed8a@gmail.com> Date: Sun, 18 Oct 2020 15:09:32 +0200 User-Agent: Mozilla/5.0 (Windows NT 10.0; WOW64; rv:68.0) Gecko/20100101 Thunderbird/68.12.1 MIME-Version: 1.0 In-Reply-To: <20201018121640.jwzj6ivpis4gh4ki@skbuf> Content-Type: text/plain; charset=utf-8 Content-Language: en-US Content-Transfer-Encoding: 7bit Precedence: bulk List-ID: X-Mailing-List: netdev@vger.kernel.org On 18.10.2020 14:16, Vladimir Oltean wrote: > On Sun, Oct 18, 2020 at 02:02:46PM +0200, Heiner Kallweit wrote: >> Wouldn't a simple unsigned long (like in struct net_device_stats) be >> sufficient here? This would make handling the counter much simpler. >> And as far as I understand we talk about a packet counter that is >> touched in certain scenarios only. > > I don't understand, in what sense 'sufficient'? This counter is exported > to ethtool which works with u64 values, how would an unsigned long, > which is u32 on 32-bit systems, help? > Sufficient for me means that it's unlikely that a 32 bit counter will overflow. Many drivers use the 32 bit counters (on a 32bit system) in net_device_stats for infrequent events like rx/tx errors, and 64bit counters only for things like rx/tx bytes, which are more likely to overflow.