netdev - Re: [PATCH v4 net-next] r8169: Add values missing in @get

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Message-Id: <20150825.141540.472110106537790402.davem@davemloft.net>
Date:	Tue, 25 Aug 2015 14:15:40 -0700 (PDT)
From:	David Miller <davem@...emloft.net>
To:	vinschen@...hat.com
Cc:	netdev@...r.kernel.org, hayeswang@...ltek.com,
	romieu@...zoreil.com, ivecera@...hat.com, nic_swsd@...ltek.com
Subject: Re: [PATCH v4 net-next] r8169: Add values missing in @get_stats64
 from HW counters

From: Corinna Vinschen <vinschen@...hat.com>
Date: Mon, 24 Aug 2015 12:52:39 +0200

> The r8169 driver collects statistical information returned by
> @get_stats64 by counting them in the driver itself, even though many
> (but not all) of the values are already collected by tally counters
> (TCs) in the NIC.  Some of these TC values are not returned by
> @get_stats64.  Especially the received multicast packages are missing
> from /proc/net/dev.
> 
> Rectify this by fetching the TCs and returning them from
> rtl8169_get_stats64.
> 
> The counters collected in the driver obviously disappear as soon as the
> driver is unloaded so after a driver is loaded the counters always start
> at 0. The TCs on the other hand are only reset by a power cycle.  Without
> further considerations the values collected by the driver would not match
> up against the TC values.
> 
> This patch introduces a new function rtl8169_reset_counters which
> resets the TCs.  Also, since rtl8169_reset_counters shares most of
> its code with rtl8169_update_counters, refactor the shared code into
> two new functions  rtl8169_map_counters and rtl8169_unmap_counters.
> 
> Unfortunately chip versions prior to RTL_GIGA_MAC_VER_19 don't allow
> to reset the TCs programatically.  Therefore introduce an addition to
> the rtl8169_private struct and a function rtl8169_init_counter_offsets
> to store the TCs at first rtl_open.  Use these values as offsets in
> rtl8169_get_stats64.  Propagate a failure to reset *and* update the
> counters up to rtl_open and emit a warning message, if so.
> 
> Signed-off-by: Corinna Vinschen <vinschen@...hat.com>

Your counter offsets should be read at probe time, not open time.

Bringing the interface is brought down/up should not reset the
counters.  Look at how the software counters behave in such a
situation.
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