netdev - Re: [patch net-next v4 0/4] return offloaded stats as default and expose original sw stats

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Date:	Fri, 17 Jun 2016 07:48:35 -0600
From:	David Ahern <dsa@...ulusnetworks.com>
To:	Jiri Pirko <jiri@...nulli.us>, David Miller <davem@...emloft.net>
Cc:	netdev@...r.kernel.org, nogahf@...lanox.com, idosch@...lanox.com,
	eladr@...lanox.com, yotamg@...lanox.com, ogerlitz@...lanox.com,
	roopa@...ulusnetworks.com, nikolay@...ulusnetworks.com,
	linville@...driver.com, tgraf@...g.ch, gospo@...ulusnetworks.com,
	sfeldma@...il.com, sd@...asysnail.net, eranbe@...lanox.com,
	ast@...mgrid.com, edumazet@...gle.com, hannes@...essinduktion.org,
	f.fainelli@...il.com
Subject: Re: [patch net-next v4 0/4] return offloaded stats as default and
 expose original sw stats

On 6/17/16 2:24 AM, Jiri Pirko wrote:
>
> The problem we try to handle is different, it's about offloaded
> forwarded packets which are not seen by kernel. Let me try to draw it :)
>
>     port1                       port2 (HW stats are counted here)
>       \                          /
>        \                        /
>         \                      /
>          --(A)---- ASIC --(B)--
>                     |
>                    (C)
>                     |
>                    CPU (SW stats are counted here)
>
>
> Now we have couple of flows for TX and RX (direction does not matter here):
>
> 1) port1->A->ASIC->C->CPU
>
>    For this flow, HW and SW stats are equal.
>
> 2) port1->A->ASIC->C->CPU->C->ASIC->B->port2
>
>    For this flow, HW and SW stats are equal.
>
> 3) port1->A->ASIC->B->port2
>
>    For this flow, SW stats are 0.
>
> The purpose of this patchset is to provide facility for user to
> find out the difference between flows 1+2 and 3. In other words, user
> will be able to see the statistics for his slow-path (through kernel).
>
> Also, as a default the accumulated stats (HW) will be exposed to user
> so the userspace apps can react properly.
>

You no longer agree with this discussion?
   http://comments.gmane.org/gmane.linux.network/346740

Essentially netdevice stats show counters for packets punted to the cpu 
and ethool -S shows h/w stats. This patch set seems to invert that.