netdev - Re: [PATCH] s2io: read rx_packets count from the hardware stats

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Message-Id: <20100628.235223.191401839.davem@davemloft.net>
Date:	Mon, 28 Jun 2010 23:52:23 -0700 (PDT)
From:	David Miller <davem@...emloft.net>
To:	mschmidt@...hat.com
Cc:	netdev@...r.kernel.org, Ramkrishna.Vepa@...r.com,
	sivakumar.subramani@...r.com, sreenivasa.honnur@...r.com
Subject: Re: [PATCH] s2io: read rx_packets count from the hardware stats

From: Michal Schmidt <mschmidt@...hat.com>
Date: Fri, 25 Jun 2010 01:32:32 +0200

> Most of the statistics the s2io driver provides in /proc/net/dev
> it reads directly from the hardware counters. For some reason it does
> not do that for rx_packets. It counts rx_packets purely in software.
> 
> A customer reported a bug where in /proc/net/dev the 'multicast' counter
> was increasing faster than 'packets' ( = rx_packets in the source code).
> This confuses userspace, especially snmpd.
> 
> The hardware provides a counter for the total number of received
> frames (RMAC_VLD_FRMS) which the driver can use for the rx_packets
> statistic. By reading both statistics from the hardware it makes sure
> that all multicast frames are included in the total.
> 
> The customer tested a patch like this (only modified for RHEL5) with
> S2io Inc. Xframe II 10Gbps Ethernet (rev 02)
> and it fixed the problem.
> 
> Signed-off-by: Michal Schmidt <mschmidt@...hat.com>

Please also use the rmac_data_octets HW statistic for rx_bytes
otherwise rx_bytes will be out of sync with the other stats too.
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