netdev - Re: [PATCH v3 net-next 5/8] net/ncsi: Dump NCSI packet statistics

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Date:   Fri, 21 Apr 2017 10:44:35 +1000
From:   Gavin Shan <gwshan@...ux.vnet.ibm.com>
To:     Florian Fainelli <f.fainelli@...il.com>
Cc:     Gavin Shan <gwshan@...ux.vnet.ibm.com>,
        David Miller <davem@...emloft.net>, netdev@...r.kernel.org,
        joe@...ches.com, kubakici@...pl
Subject: Re: [PATCH v3 net-next 5/8] net/ncsi: Dump NCSI packet statistics

On Thu, Apr 20, 2017 at 05:26:14PM -0700, Florian Fainelli wrote:
>On 04/20/2017 04:38 PM, Gavin Shan wrote:
>> On Thu, Apr 20, 2017 at 01:21:03PM -0400, David Miller wrote:
>>> From: Gavin Shan <gwshan@...ux.vnet.ibm.com>
>>> Date: Tue, 18 Apr 2017 16:51:32 +1000
>>>
>>>> This creates /sys/kernel/debug/ncsi/<eth0>/stats to dump the NCSI
>>>> packets sent and received over all packages and channels. It's useful
>>>> to diagnose NCSI problems, especially when NCSI packages and channels
>>>> aren't probed properly. The statistics can be gained from debugfs file
>>>> as below:
>>>>
>>>>  # cat /sys/kernel/debug/ncsi/eth0/stats
>>>
>>> There is no reason you cannot use ethtool statistics to provide this
>>> information to the user.
>>>
>> 
>> It can be dumped by ethtool, but it's more reasonable to dump them
>> through debugfs for couple of reasons: (1) ethtool usually dumps
>> statistics collected by hardware, but this debugfs file dumps the
>> statistics of packets seen (collected) by software. They are different
>> things. Note that NCSI channel collects statistics in hardware and it's
>> not exposed or dumped by this patchset. They are candidates for ethtool.
>> (2) To expose this through ethtool relies on the availability of the tool.
>> It's nicer not to depend on it. (3) This interface can be used to check
>> the debug packet has been sent successfully through /sys/kernel/debug/ncsi/eth0/pkt,
>> dumping the statistics through debugfs make this (debugging) mechanism
>> consistent.
>
>Can't you create a ncsi folder under /sys/class/net/eth0/nsci/ and then
>put your stats in there? That would at least look slightly consistent
>with what is already existing for the non-NC-SI networking stack.

Do you think it's good place to have /sys/class/net/eth0/ncsi/pkt?
Note this file accepts commands to send NCSI comands and dumps the
corresponding response on read. Also, it's a debugging interface
and disabled (invisible) for the most time. I think all directories
and files in /sys/class/net/eth0/ should be visible and the structure
is stable all the time.

Actually, I used procfs initially and replaced by debugfs according
to Joe's suggestion. I think debugfs is good enough for this case.

Cheers,
Gavin