netdev - Re: [PATCH v4 net-next 06/10] net/ncsi: Ethtool operation to get NCSI hw statistics

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Message-Id: <20170504003838.GA16780@gwshan>
Date:   Thu, 4 May 2017 10:38:38 +1000
From:   Gavin Shan <gwshan@...ux.vnet.ibm.com>
To:     David Miller <davem@...emloft.net>
Cc:     gwshan@...ux.vnet.ibm.com, andrew@...n.ch, netdev@...r.kernel.org,
        joe@...ches.com, kubakici@...pl, f.fainelli@...il.com
Subject: Re: [PATCH v4 net-next 06/10] net/ncsi: Ethtool operation to get
 NCSI hw statistics

On Wed, May 03, 2017 at 08:16:43PM -0400, David Miller wrote:
>From: Gavin Shan <gwshan@...ux.vnet.ibm.com>
>Date: Thu, 4 May 2017 10:05:34 +1000
>> On Wed, May 03, 2017 at 09:18:23AM -0400, David Miller wrote:
>>>From: Andrew Lunn <andrew@...n.ch>
>>>Date: Wed, 3 May 2017 14:47:22 +0200
>>>
>>>> On Wed, May 03, 2017 at 02:44:37PM +1000, Gavin Shan wrote:
>>>>> This adds ethtool command (ETHTOOL_GNCSISTATS) to retrieve the
>>>>> NCSI hardware statistics.
>>>> 
>>>> Hi Gavin
>>>> 
>>>> I've not been following this patchset, so maybe i'm about to ask a
>>>> question which has already been asked and answered.
>>>> 
>>>> Why cannot use just use ethtool -S for this?
>>>
>>>Indeed, when I said to use ethtool for these NCSI hw stats I meant
>>>that the "ethtool -S" be used, not some new ethtool command.
>>>
>> 
>> Thanks for the comments. Feel free to ask any questions which would
>> make the code clear and better. There are couple of factors I thought
>> separate command is better than ETHTOOL_GSTATS: The statistic items from
>> ETHTOOL_GSTATS are variable, meaning the kernel needs provide the layout
>> of the statistic items via ETHTOOL_GSSET_INFO and ETHTOOL_GSTRINGS.
>> NCSI HW statistics aren't following this and their layout is fixed.
>> Besides, statistics for ETHTOOL_GSTATS are maintained in local MAC,
>> but NCSI HW statistics are collected from NIC on far-end. So they're
>> different from this point. Lastly, the NCSI software statistics needs
>> separate command. It'd better to have separate command for HW statistics
>> as well, to make things consistent.
>
>ETHTOOL_GSTATS are for device specific statistics.  Whether they are
>fixed in your implementation or not.
>

For NCSI HW statistics, they're always fixed. It's assured by NCSI
specification. It seems my explanation isn't convincing enough. I'm
fine to convey NCSI HW statistics through ETHTOOL_GSTATS (ETHTOOL_GSSET_INFO
and ETHTOOL_GSTRINGS). Dave, please confirm it's what you're happy to
see?

Cheers,
Gavin